If I had a nickel for every time I was in this situation.....
TIP #0
Really important: tell them "If sitting inside for four hours on a lovely summer day with five other people doing pretending to be elves and wizards doesn't appeal to you, or can't hold your attention, Pen-N-Paper RPG's probably aren't for you."
TIP #1
Make the characters for them beforehand, but ask them what kind of characters they might like to play. Make a diverse set of level 1 archetypes (when I did this, I took the iconics from the PHB and gave them as characters, but you might want to gender-swap a few since people generally like to play chars of their own gender). The ones who've played before might be fine rolling up their own -- make sure they have them by the time they get to the table. Nothing says "don't try this again," like spending 4 hours going through and explaining character creation. Do it for 'em (but make sure to give them a wide selection of types), and just say "Don't worry about understanding what it all says right now, I'll explain the things you'll need as we go along." Get RIGHT into the action. Make the story spur *instantly*.
TIP #2
Be easy on the combat. Because combat is complicated, and complexity throws newbies. Do something archetypal -- they fight goblins, they fight giants, they clear out rats from the sewers, whatever. But don't make it complicated and tactically involved. Having only 2 or 3 encounters is a good thing, especially if the last one is the "boss encounter" where they can beat the bad guy and save the day.
TIP #3
Keep the story stereotypical. Goblins have kidnapped the princess! The rats have grown to DIRE SIZE! The Ogres are attacking trade caravans! Something quick and easy to understand that can give them a feeling of what it's like to play a typical game. The big boss should be the goblin chief, or the rat that's at the source of the mutagen, or the human wizard who's been manipulating the ogres. Once he's dead, that's the adventure!
TIP #4
Have them gain a level. Really, it's a good hook for bringing 'em back. It's a rush, it's a reward, it's a power trip, and it's surprisingly addictive.
TIP #5
Don't assume they won't come back. The first few posts sound very "I know exactly how this is going to go," and kinda like you're only being goaded into it. If you're not into it, don't do it. Your enthusiasm is what is going to keep them interested, and if you're not enthused about running the game (because they're only gonna drop it or whatever), tell them to find someone else. I could be wrong about your mindset, it's just the impression I got FROM THE INTARWEB, but don't do this unless you're totally into it, or you won't just hurt your game, you'll hurt the first impressions of these potential lifelong players.