A Simple Will needs two witness and one executer.

Google "Will Kit", you can learn some basic knowledge. Then contact a lawyer if your will is very complecate --- especially if you think someone might challenge your will after you die. A lawyer is able to make things solid and complete.

Tips for a simple will ---
(1) Avoid this kind of term "Give .. to my wife" , or "Give .. to my father". Put the names directly in the will. Or they have to provide extra documents to prove that they ARE your wife/parents.

(2) Your closest family might be the most posible people with you when an accident happens. They might be injured or die too. Add paragraph to deal with this situation ---
You do not want your wife's bothers get everything, just because your wife dies one minute later than you in a car accident. But, you also want to give her everything in case she survived from the accident.
Put this in the will --- you give everything to your wife. But if your wife dies within "10 days" of your death, you'd like to give everything to your brother.

(3) Name a person to fully represent you when you are very sick but not die yet. say, he might need to make a decision to sell your house to pay your medical bills. he might need to make a decision to discontinue your treatment if you are in a vegetable state for a month. This person is called "Power of Attorney".