I would say that there are 3 main things you have to remember when going into the swamp for the first time.

1. You have the recipe for poison resist mead now. Take it as soon as you arrive. The resistance doesn't apply to poison that's already in your system, so you need to take it before you get hit.
   
   
2. Oozes and skellies are two of the most common enemies in the swamp, and they're vulnerable to blunt damage. Even if you're a sword or spear main it's worth brining a bronze mace or a maxed out stagbreaker into the swamp. The stagbreaker in particular is useful as you can use it to attack around corners in crypts or hit leeches from the safety of the shore.
   
   
3. This is the biggest difficulty spike in the game. There are monster spawners strewn about and now there are also the tough-ish abominations skulking about. One of the best ways to survive in the swamp (especially early) is to keep moving so you don't get bogged down and go around the spawners instead of through them.