The tips i can give you for a short campaign are these, may be dissapointing judging by the form of answers you are waiting for, but give it a read.
The first thing to do is to make up your mind, if you want to use these sessions as a campaign opener or not. Ask your friends if they could play during the semester, or if they are willing to continue in the next break, or whatever seems appropriate.
If you choose to continue it, you should probably choose a light and friendly, yet full system (i would suggest the essentials of DnD 4ed, but i have never played with these books, just read some of them). There is always the possibility to choose a more "heavyweight" system, since you will play again. Ask your friends what they want to play, or present them with some systems (if you want recomendations i have some in mind, not all tested though, ask with a comment)
If you choose not to use these sessions as a campaign opener, i would advise taking a look at Everway. It is a light system, with four base atributes, simple character creation, and the best about it, powers and magic are not defined, they are made by the players (DM discretion advised). Personally, i find the concept great, but the setting could use work. Also look it up on wikipedia, for a more "wide" viewpoint.
Step 3 (but maybe it should be step 1)
Gather your friends for coffee/beers/margaritas/whatever you like, and discuss with them, what they want to play (as a character), if they want to continue playing, and all the aspects mentioned above (and of course the ones you think about). Make a decision together and have fun playing
ATTENTION:While Everway is not hard to "sell" with "Dude, you can play WHATEVER you like, WHATEVER!", it does not have a level or advancement method, if i recall correctly, thus it is presented as short-campaign option. Give it a look before you put it on the table, it could mix things up.
Also, for the time wise thingy, you can use a solid reason for your players to cooperate if they dont know each other (throw them in an arena, i know i loved it when i used that:)), or, if they like, make a party of adventurers that have been travelling together for long.
Also, keep things "fast" through the beauty of simplicity. There is no need to describe every inch of the paladin's armor if it is not crucial for the plot/storyline. Lastly don't try to stick every good idead you had in the campaign, simple but intriguing plots are best, no need for incorporating that Abominable Psionic Techdracolich with three templates from Manual to the Monsters of the High-Low Left-Right Tyranical Psychosocial Kingdom of Gherstheinerbag. ( I am exaggerating i know, i will stop now.)