Make a road. It will solve everything at awamp.

I would also recommend wearing Troll Armor with a Bronze Buckler, as you're going to have the "Wet" debuff pretty much the whole time you're there. You'll be able to move faster and avoid the deeper puddles with Leeches. The buckler is for the Archer Draugr and Skeletons who'll snipe at you.

You would also do well to hit up your Trader and obtain the Dverger Circlet and Megingjord. The crypts are dark, and Iron ore weighs a little more that Copper, so the additional 150 carry weight comes in handy hauling loot. Also, I like to bring both my Antler and Bronze pick axe when going in, using Bronze first and Antler as a back-up.

You only need 10 Bones to summon Bonemass and they weigh a decent amount. You'll find them in chests, on the ground and in the mud piles. Once you get 10 you don't need to worry about them unless you want to kill Bonemass multiple times. (Just to save on carry weight).

If you play with friends, I would have one person carry all the gold/rubies/amber, yellow mushrooms, etc. And the others carry as much ore as they can, increasing how much you can take back to your boat. Recommend having a Longship as well for the large storage capacity.

Not sure if anyone mentioned it but stagbreaker is your friend in the swamp.

kill 2 abominations and get the mask asap.

Before going through water, stop and look around for telltale signs of leeches. Also, trust no sound. ALWAYS look around. If at night (God help you), look up and around for Wraiths.

You absolutely need poison resistance potion. That's the base.

And keep in mind that it's a poison RESISTANCE, not a CURE. Once you are poisoned, it is too late. You need to take it before entering the swamp or at least, before entering a sunken crypt or when there is enemies that you are about to fight.

From this, you'll figure out the rest.

not wanting to spoil anything all the recommendations above are excellent but I would suggest to also bring your best axe and fire arrows.

Don't get ahead of yourself, take your time, don't let yourself get overwhelmed by attracting too many enemies. Approach from angles where you can kite enemies easily, my swamp allows me to approach from high ground, hence I'm able to overlook the battlefield before I enter. Keep an open eye for enemies and muddy scrap piles you can rarely find them outside of swamp crypts.
I can't offer any other advice because I haven't "completed the swamp yet", at the same time I haven't died in the swamp. So good luck.

P.S. You can lure tolls and other enemies into the swamp, makes for some interesting fights if your close to dying as then they whittle their numbers down.

Whenever you find geyser, dig the area around it until it is covered by water. Mark it on your map. Whenever you pass by the area the surtlings that spawn there will die instantly from water damage, dropping sturling cores and coal. If you can find 3 or more geyser near each other this can replace charcoal kilns entirely.
Craft an iron Mace. Most enemies in the swamp are either weak or neutral to it (including the boss) and it will serve you well even in the mountains later against golems.
The only blunt-resistant enemy in the swamp is the abomination, you gotta use slash weapons on it.

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.

My advice would be to avoid running in. Scout the edges for resources, run in to grab stuff then run out. Don't overextend too fast... it can get ugly really quick. Mark stuff on your map so you can plan it out when you get ready.

My tip is this: much of the fun of the game comes from figuring it out for yourself. Play safe and learn the lessons available and you'll be fine.

Leech, Blob and Oozer (nightly mob) cause poison dot.
So have some poison resistance mead with you.

At least take some poison potion and go slow at first

1.) use poison potion before you get poisoned (best all the time if you are new to swamps) - 1 mead = 6 flask = 1 hour fun in swamps
2.) remove all spawn points..
3.) avoid night
4.) chop down as many trees as you can
5.) flatten gound to make a save road back home
6.) only go out with rested buff
7.) use health potions
8.) use stamina potions
9.) use best food you have

As others have said, its a fun area to experience initially though with difficulty.
I will just say try not to be caught in the night when you first start exploring.