The only things I've really figured out to sell all the time because they are completely useless is cigarettes. What about Pre-war money and NCR money? Is there any reason to hang on to it or should I just sell to vendors? What other things should I pick up to sell that don't really have any other uses? I generally try to pick up just about everything for when I figure out how to do recipes and make stuff (food, weapons, etc) but right now my level and skills are too low to do much of any of that, so I'm just hoarding. But I hate constantly being bogged down and having to fast travel back to my dumping point, I'd much rather figure out which things I should just sell outright, and which things are worth carrying around the extra weight for when I need them. I don't like hoarding stuff and dumping it somewhere (Victor's shack), but I'm afraid that if I don't, I'm gonna miss out on something down the line.

This is kind of a difficult question to answer for someone else. What will be useful to you will depend on your character build . But the best way to figure that out is to stop at work benches, reloading benches and campfires and scroll through the recipes, check the ingredients and the skill requirements.

Strongly recommend memorizing the components for weapon repair kits, and once you can build them save them for your rare/unique weapons.

Desert Salad is probably the best meal because it's light weight and restores a lot of HP ( depends on Survival skill ).

These are generic suggestions because I have no idea what your character build is , but hopefully that helps.

Just study those recipes and decide what's going to be useful for your character, dump the rest on a merchant.

...Or end up buried alive in Victors shack under piles of hoarded garbage.

I pretty much just save the makin's for repair kits and specific ammo reloads, and sell or leave the rest. After you get past the first bit of the game, where you ain't got squat and so grab and sell every toaster and shot glass just to have a few caps to rub together, I don't bother picking up anything that doesn't value for at least 20 caps. Saves on hauling a lot of worthless junk around that don't sell for anything much. A lot of the crap layin around in the game has some use or another, even if it's just a solitary one-time use for a quest item, or a crap crafting recipe that nobody bothers with. Go to the Fallout NV wiki, and search on the item name, if you want to know if it's ever really good for, or used for, anything. That place is pretty comprehensive.

As said above it's hard to specify what to keep and what to sell.

I am a roleplayer, and some of what I keep is worthless crap, but I will let you know.

Weapon Repair Kits (I save all materials to make them, from the beginning of the game).
All Meds. Every single one, even if I don't really need it.
Cigarettes. I save them and put them in my house. I am a smoker IRL and if our world became like the Fallout Universe I would like to have them.
Nuka Cola, Sunset Sarsparilla and all alcohol and fresh water. Once again, as an RPer, I'd like all this stuff in my fridge. On hardcoe mode I will take the water with me.
I save Teddy Bears to throw on my bed.

Everything else I pretty much sell. At 20 hours in the game, I had about 30,000 caps without even selling half the crap I find. I don't pick up cups, or books or anything like that.
On my current playthrough, (46 hours), I have around 90,000 caps and over 200 nuka-colas, over 600 sarsparillas, 30 teddy bears etc.

Only advice I can give: Collect what you need. Look up recipes and collect those items.

The currency can be sold for money or kept to trade with. Either way you can get rid of them at a merchant. In terms of junk, it depends on whether you can and will use it for crafting.
Like people have said, check the recipes and compare the requirements to what you plan in regards to your skills.