If you are a full aged and capable person able to reasonably determine your actions and clearly express your intentions you entitled to be a testator. You have to draw your will only personally. A will shall not be made through an agent. 
You have several options to draw up your will: (i) to write a will in your own handwriting and sign it (Holographic Will); (ii) to sign the writing composed by other person, declaring before two witnesses that it is his/her will; (iii) or go to notary and tell him how do you want to make your will, and notary applies legal form to your statement of last will. You do not need to show any documents about property, which prove that you are an owner. 
All aforementioned forms of will could be deposited at notary so that they will be preserved and guaranteed to be submitted to the competent notary which, in due time, would conduct the succession procedure.

If you make notarial will or deposit your handwritten or written will before witnesses to the notary you can be sure that your will would be safely kept and after testator death will be submitted to the notary which would conduct succession procedure. Every will drawn up by the notary is registered at the Will Registry at Notary Chamber of Montenegro. Furthermore, the Notary Chamber is not entitled to reveal any information about the existing of the will before the testator death.

Every notary conducting the succession procedure will apply to the Notary Chamber for information whether the decedent made will which is registered in the Will Register. Having in mind that all the wills drafted by the notaries are registered in the Will Register, there is no possibility that the will drawn up by the notary remains unrevealed in succession procedure if it exists

Testator is entitled to select the law of the state whose citizenship he/she possesses or the law of the state in which he/she has the habitual residence in the time of selection of applicable law or in the moment of his/her death as applicable law for the inheritance of his/her entire estate.

When drawing up your will you are free to favour any heir. However, you should be aware that Devisor is not entitled to dispose with his/her estate in the entirety because there is part of the estate that is not disposable by the will, and it always belongs to the certain legal inheritors (wife, children, parents…). You should address the notary in order to evade possible misunderstanding among your heirs.

You can favour your spouse like you can freely favour any other heir, i.e. by drawing up a will. However, you should be aware that there is part of the assets that is not disposable by the will, and it always belongs to the certain legal inheritors (wife, children, parents…) despite the provisions of your last will. Also, you can make a marriage agreement (which must be drawn up by notary) defining the matrimonial property and allocating your spouse’s share in it. 
The partner from long term extramarital partnership (lasted at least three years or less if you have child with him/her) has the same position concerning the inheritance rights as the spouse. However, if you want to favour your partner you can take the same measure as favouring your spouse. 
For further advice you should address the notary or lawyer.

You are entitled to exclude some legal heirs from inheritance. However, you can do it only for specific reasons provided by the law. These reasons are: serious improper behaviour of the heir to the testator; committed premeditated criminal act to testator, his/her spouse or child; conducting immoral life. Testator is not obligated to indicate a reason for debarring from inheritance, but it is useful to indicate, for the sake of easier prove of the legal conditions exist.
Law on Succession of Montenegro also recognises the reasons for obligatory debarring the heir from inheritance, and these reasons are ex officio monitored by the competent body conducting the succession procedure. These reasons are: if heir deprived decedent of his/her life; if heir forced or tricked devisor to compose the will or to recall the will already composed; who destroyed, forged or hid the devisor's will in order to prevent his/her last will to be realized; who denied his/her legal obligation to support decedent or the one who deprived decedent of urgent help that was needed. 
For further advice you should address the notary

No. The will is individual legal act. Furthermore, the Montenegrin law does not recognize so called mutual will between the spouses, neither.

According to Law on Succession of Montenegro the heirs belong to four orders of inheritance. The members of the previous order of the inheritance exclude from the inheritance the members of the former orders of inheritance. The Representation rule applies, which means that the member of the previous order of inheritance that had deceased before testator is inherited by his/her descendants, and so on. If the deceased has not drawn up the will, the heirs of first order are spouse and children inherit equal shares of the assets. If there’s no any heir of first order, heirs from the next order of inheritance inherit the assets

The only specific objects with regard to Montenegrin succession law are furniture and other household objects which always belong to the spouse and other decedents' heirs who lived with him/her. 

You can prove that you are heir by handing in relevant documents (e.g. birth certificate, marriage certificate, birth certificate of your antecedents etc.) to the notary. If the documents is justified the notary will conduct the succession procedure and issue decision on inheritance.

Montenegrin law does not recognise the concept of the priority heirs. 
Rregardless of the content of a will children, spouse and parents of a testator are entitled to the compulsory portion of assets that shall be one half (children and spouse) or one third (parents) of the portion to which each of them would have been entitled by the inheritance on intestacy if their order of inheritance applies (reserved portion).

Inheritance of decedent's assets include the aggregate of both of property rights (assets of the estate) and liabilities (liabilities of the estate) of a decedent up to the moment of his/her death but only up to the value of inherited assets. The same general rule applies also when there are minor children among the heirs.

In the event of intestacy surviving spouse inherits the equal share as the decedents children as members of first inheritance order. If there are no children the surviving spouse is transferred to second inheritance order and inherits one half of decedent's assets and parents and their descendants inherit the other half of decedent’s assets. The surviving spouse inherits the entire estate if there are no surviving members of second inheritance order.

An inventory is not usually obligatory. The inventory of the deceased's assets is carried out on the basis of the heirs' information. An heir who has accepted an inheritance may request an inventory and the notary is obliged to describe all things that the estate includes. In this process the notary evaluates the assets with the commercial value and makes the deed on inventory, which must be signed by the attendants and the notary. 
The decedent’s assets are usually evaluated by the heirs' statement, but if parties declare inappropriate value of assets, value may be determined by engaging the court expert establishing the market value of the objects. For Detailed information ask your notary.

An estate include the aggregate of both property rights (assets of the estate) and liabilities (liabilities of the estate) of a decedent as of the moment of his/her death. The heirs will only be responsible for the deceased's debts up to the value of assets they inherit.

Yes, an heir may renounce the inheritance when giving his/her inheritance statement before the notary. 
General rule is that heir accepts the inheritance under the benefit of inventory. The heirs will only be responsible for the deceased's debts up to the value of assets they inherit.

If an estate requires administration or if the decedent’s creditors have filed a claim, the notary shall appoint the temporary administrator of the estate. An administrator shall not be appointed if at least one of the heirs has accepted the estate or if an executor of the will has been appointed. 
If the deceased made a will about their assets, the deceased's assets will be divided as it was ordered in the will, but In the event of intestacy, the heirs shall inherit the shares depending on their relation to decedent. The heirs may mutually agree on division of the estate pursuant to their respective shares and in that case the notary shall their agreement insert in the decision on inheritance. 
Ask your notary for detailed information about it.

Taxes on inheritance and donations differ in relation what kind of property is subject of inheritance or donation. For Detailed information ask your notary.

The general rule is that the heirs of the First order of Inheritance do not pay the taxes on inheritance neither on donation. The heirs of second and further orders of inheritance pay the taxes in accordance with the ordinary regulations on taxes on transfer of property (real estate, vehicles, etc.). For instance, the tax on inherited real estate is calculated at the rate of 3% of the market value of the real estate. 
Ask your notary for detailed information.

The Taxpayer is obliged to declare income by inheritance within 15 days from the day the decision on inheritance becomes final and binding. The tax is due to be paid within 15 days from the day the tax authority issues the decision on taxation. (Usually one month since the income declaration)