Before you people get moral and righteous on me, as the art of war says once you become(or master how your enemy thinks) you can protect yourself from that enemy.
The Skills Assassins Acquire
1.) Learn to speak several languages fluently.
2.) Learn to use knives first. Knives are more effective then guns in close combat. A good marital art to start with is filipino marital arts.
3.) Learn to use guns. Obviously to an assassin silencers can be your best friend, if you do not ave a silencer on hand a pillow would do. For the layman a silencer is what you put on the gun so that outside people do not hear any sounds.
4.) Learn how to get into areas of countries that do not have electric cameras at their points of entry. Most airports do but surprisingly alot of borders where you can enter by foot do not.
5.) This may be tough but some time in the military helps. Alot of the best assassins were ex military people.
6.) As A cover try to get a profession that allows you to travel overseas.
7.) Low key, Low key, No fancy cars, no fancy homes, casual clothers is best.
8.) A family is not possible.(if you are smart). Never have anything in your life that you cannot walk away from in 60 seconds.
9.) You need to have more then one passport. This is essential. In alot of third world countries it is easy to purchase a passport. Yet you want some first world countries passports because it gives you more options. Some third world passports you might need an additional visa, which is more paperwork.
10.) Always be able to work with cash only. Have jewelry on hand just in case you have to wear a watch to cross the border and then sell it for money.
11.) One of the best martial arts to learn is israeli marital arts. Oriential style marital arts mix alot other elements into it, israelis just go for the kill.