I want to make a campaign... How the heck do I do it?

Basically what it say on the label. I want to create a good campaign that players might enjoy, but I don't really have much experience or resources to work with. Any suggestions for what might be easiest/best for a complete newbie who's trying to make a world?? I'm familiar with D&D 3.5 and 4e.

First before anyone can give you advice, you might want to let us know what system are you familiar with. After that you might want to let us know what tone you are looking for. Say you are familiar with 3.5E D&D even though you are new to it and you want your game to have lots of magic and such. IF that is the case people could give you suggestions to look into  but if you are wanting to make a campaign for a slapstick cartoon then most suggestions for the 3.5E system wouldn't work. Understand? So tell us a little about your familarity with gaming in general and what type of theme or such are you interested in running.

I'm semi-familiar with 3.5e and 4e D&D, and I've sat in on a couple of games of each. A friend and I had an idea to make the setting a Street-Fighter style tournament, have the PCs as entrants? Mostly martial, close-up combat, all magic would be buffs; strength, speed, etc. Sound doable?

Sounds like you'd have ability enhancements like Cat's Grace, Bull Strength, etc. I've ran games that had tournaments or something similar.

Yeah; I was thinking of having those in equipment form... Boots of Cat's Grace, or something of the sort. The effect would be less potent, but passive.

Well now we have something to work with. You are familiar with 3.4 and 4e. Do you have the books or pdf's? Have you been to any SRD sites (System Resource Documents)? There are few for various systems so step 1 is finding you your resources. Step 2 is working out a brief setting. You are wanting an arena or tournament based setting. Is this just going to be just tactical (nothing but your mini and your sheet for dicerolling) or more roleplaying aspect of it. I know people will say you are roleplaying no matter what you do as long as you are interacting and they are correct but I'm just trying to help you figure out if it is going to be mostly combat or is there going to be most non combat or just a 50 / 50 blend or somethings else. Step 3 is the hard part. Deciding what you are comfortable with in the terms of allowed mechanics. Some people restrict to specific books, others restrict only specific classes or races or even equipment while others are comfortable enough with their knowledge of the system not to restrict anything. Step 4 is putting it all together in your gameboard so that people can use it. Step 5 is listing it in the LFG search and here in the forum. Step 6 is usually the last step and that is just running the game. Hope this helps.

Step 3 is actually reasonably easy in 4e. There's actually a sidebar in the DMG about using the rules for a Wushu style game, where, whenever the mechanics say you teleport, you really just did a crazy fast martial arts running thing or performed some extreme feat of acrobatics. You can actually push that further and apply similar abstractions to the gear: what would be a fighter in full plate wielding a sword and a shield (high AC, low speed, d8 damage die, etc.) would simply be a character using a style that emphasizes those attributes, such that, in game, the character is dressed in a gi and unarmed, while mechanically identical. You can even have the magic using classes behave in much the same way, just replacing whatever kind of magic they're using with ki, while still having them be effective in combat because 4e allows you to use Int or Dex for your defenses (so a Wizard actually has a reasonably decent AC, even if it's lower than a fighter's because they're in cloth). Of course, 4e is pretty explicitly a game of team based combat. 1v1 doesn't really turn out well because only Strikers are really designed to not help their team (leaders are borked as *hell* in 1v1 because they have their healing and defenders are problematic because they're designed to protect allies, which means that a lot of their mechanics are wasted when there's no one to protect). If you're going for a 1v1 fighting tournament, 4e is definitely not the right system to use (unless explicitly say no to Leaders and tweak some of the other stuff).

Just be careful what you plan, you need to have enough stuff prepared that you are ready for fights, traps etc. Mostly importantly you need to be able to improvise, if you plan to much and the players do something unexpected you will basically sit there drooling on yourself while you try to figure something out. I'd suggest having a couple of stat blocks on the side that you can use in a pinch if the players do something unexpected. 

Okay, so in answer to this stuff: I found pdf versions of all the books I'm going to need. Step 1 complete. I'm definitely running 3.5. And for contingency plans, I'm going to A) Trap the hell out of the arena, B) Allow teams or have zerg-rush type battles, or C) Some third thing I haven't quite thought of yet. P.S: What are stat blocks?

it is just a listing of the mechanics that each character will have. the stats, the attack bonuses, AC, HP, saves, etc..  There is nothing in the block of mechanics to roleplay with much. it is just the crunchy number stuff.

Whenever I'm building a campaign of the sort you're building there, I would use the first many rounds of combat to set the premise and teach them the rules of the game. I.e. the first 5 rounds would be one opponent for each PC, getting progressiely harder. Then I would introduce a little twist, like a shooter, og a gang mob. Or something like that. Then go back to the, by now, familiar style. Then slowly mix it up to keep it interesting, so the players won't get bored. One round where all the people in the arena are blinded (so the audience can still watch, but everybody fight blind). One round with an invisible opponent. One round where the arena is flooded, either in one man-ships or swimming and there is an underwater opponent. One round with the-floor-is-made-of-lava mechanics. Etc etc.

This is going to be awesome!

Glad to hear it is shaping up nicely for. See if you give people an idea of what you know and are seeking they can help you.

Thanks, everyone! I'm going to make this awesome thanks to your help!