When I was eleven years old, it was a very good year, and I can remember my daily routine vividly. These were the years before I owned a Sony Playstation, and I used to venture to my friends house - everyday after school - to watch him play through Final...
Don't stay in one place for too long if there are snipers about.
You can jump back towards walls you've already jumped off to avoid obstacles.
In the end-of-level scraps, take out anything with a gun before you deal with the others.