Now there are some annoying details you have to fulfill, including standardized tests (Americans love them for admissions, don't know why, but I guess makes life a little bit easier for admissions committees)
First the GRE. It's possible to take it all over Europe (doesn't matter in which country you take it, so you may look abroad to find a closer location, check out www.gre.org, explains the whole process). But beware, they usually have quite a waiting time till you get a slot. Try to take it as early as possible, this may allow you to take it again and the company also needs quite a bit of time to come up with your final score.
The test has three parts, a quantitative, verbal and a analytical part. The verbal part is mostly irrelevant, nevertheless try to do it as good as possible, otherwise you might raise eyebrows with regard to your english knowledge. (So a low score should not be a reason to repeat it)
The analytical part are now two essays, one a regular one in which you have to argue a given statement. For the second essay the test will give you a statement, and your task is it to argue about the logical and argumentative quality of the statement. If you are used to write in English, you should be fine, otherwise do a certain amount of training for it. This is not the most important part of the test, but a too low result again is not really helpful. (I only got a 4.5 and still got into a top school, however some people posted in an internet forum, that UC's (Californian Public Universities like Berkeley, San Diego) and other public schools may have a minimum requirement of 5.0 or higher)
The absolutely most important part is the quantitative section. Consisting of short math question, it can be solved with high-school math knowledge. However definitely do some prep tests before to get used to the type of questions they asked. Try the exercise tests ETS has on their website, but beware I found them much easier than the real test. You have to score at least high in the mid-700 hundreds to have a shoot a decent place and for a top-school you should have at least 780, more likely even 800. I guess some of the top-schools have limits ranging from 730 to 760 which are a must and they don't even read your application if you don't have that. If you are not satisfied with your results, you always can repeat the test. Costs a lot and may cause deadline problems, so better be prepared for the first one.
Second the TOEFL. This is absolutely the most annoying part of the whole process. Unless you studied in the US or UK (but even then it is not guaranteed), schools will ask you to provide the TOEFL to guarantee your English knowledge. This test is just plain stupid, but still you should have a look at it before you do it, otherwise you actually may not score high enough (ok, I did that thing once in high school and got enough, so it is definitely not very hard, ). The organizational procedures (see www.toefl.org) are the same as for the GRE (as are the costs), so act accordingly.
Third, transcripts Now the main problem here is to get an English translation. This I guess depends very heavily on customs at your home university (mine issued them for me), so I can't give you much of an advice here. Check websites at schools for exact requirements, maybe find current grad students from your country and has how they did it.
One thing which you might want to include is a description of grade scales at your school, especially if you are studying in a smaller country. Most schools will have experience with European grades, but this is not a guarantee. It also can help if your grades do not always look as if they were good (at my school, a 10 out of 10 basically never happened, a 9 was extremly rare, and 8 still excellent, now compare that with US-GPA's of 4.0 out of 4.0). If you include such a description, always try to get an official at your school to sign and stamp it, maybe even directly include it with transcripts.