I'll try to help as best as I can, since I've played MGS2 more times than I can count.
The only tip I can give you for now is use your first-person view to survey the environment and see things out of your regular line of sight. Press up against walls and use corner-look as much as possible to get a good idea of where any enemies are, and keep an eye out for any and all hiding places. Find enemies, learn their patrol routes. Keep an eye out for what enemies have radios. Try to find the node as soon as possible so you can get linked up and get your radar online.
If you got the thermal goggles, looking out for enemies is a lot easier. It's been a while since I've played, but if you don't have the thermal goggles, I believe they're in the pool of water you start out beside right at the beginning of Raiden's part.
Can't really give much more help than that without knowing where you are.