I've attempted to, but people always managed to find a way out. Since you've already plotted out your campaign, it's probably pointless advice for you personally, but since this is a D&D thread there are some common pitfalls newcomers might find hard to avoid - I know I did.
1. It doesn't really matter if you pick 3.5 or 4e, as long as you end up playing the game. Like with vi and emacs, people will find good and bad sides about either. There's no best version, don't spend too much time on it.
2. If you just want to try the game out, there's freely available campaigns everywhere.
Some are even official.
3. If you can't remember all the rules for specific situations, that's alright - D&D is designed with house-ruling in mind, so the Dungeon Master can make something up on the spot he or she sees fit, as is their authority. You can look up the actual rules later on, the important part is to keep the game going.
4. If you have a bunch of friends but they're living all over the place,
Maptool is an excellent framework for tabletop RPGs, although there's a fair learning curve. It's not the same as having friends around a table, but it does work.
Some more practical advice for you as a DM, even though it's hinted at or even straight-up written in the rulebooks, I found it important enough to take these out separately.
5. I find this the
most important one - remember at all times that D&D is a collaborative storytelling effort. A common first-time DM mistake is to plot out everything and leave too little room for the players' own additions to the story. Your players might want to do something else than you intended entirely, and that's okay! Make sure you offer sufficient room for them to tell a story as well, and don't control the characters' actions too much, either directly or by hinting at what they should be doing. Describing scenarios works better than being the narrator to an ultimately linear story.
6. Prepare a bunch of throwaway dungeon maps. As mentioned in 5, your players will do unexpected things. If you have a few - say, three to five - simple dungeon or cave maps handy, not only will you be able to let your players head out of town, but you can give them cool stuff to explore. This makes for a more polished and enjoyable experience. If you're really going all out you can work on some lore that you can fit into more than one situation, like specific wall paintings or artifacts that you could put anywhere, but tie in with the main story so it doesn't end up feeling cheap or disconnected.
7. Props are great! If you have the benefit of a real life setting, you can prepare some maps to hand out to players, or fake wanted posters, or magical artifacts (cheap spheres made of coloured glass or plastic). This has the added benefit of encouraging players to interact with them in the game more often, and helps visualize the experience.
That's all I can think of off the top of my head. Best of luck in your games!
