Mannahnin
Scion of Murgen (He/Him)
Always use and provide pregenerated and pre-equipped characters. With rare exceptions, the generation process always takes more time than optimists think. Ideally provide twice as many (or even more*) as the players you expect to have, so everyone has options and if you're playing a combat-heavy session you have spares and can potentially give them a whole new set if they get unlucky and TPK early. 
To save even more time, don't hand out the character sheets to be picked from. Players will spend too much time reading over their options. A better option is to give them a list of characters with just the basics like race & class. If it's a more character-centric game having names with portraits is great. I also recommend an in-character quote. A pithy piece of dialogue. One of my favorite convention DMs does this. Has the players pick characters based on a card showing a picture, a quote, and the race & class, so people don't burn a ton of time looking through character sheets in detail. He also has everyone roll a d20 for pick order, again to speed things up and counteract the tendency of some players to be polite and defer and slow down the process.
*(When I last ran B/X at a convention I expected a table of 5-6 players but offered 14 pregen options; 2 of each class).

To save even more time, don't hand out the character sheets to be picked from. Players will spend too much time reading over their options. A better option is to give them a list of characters with just the basics like race & class. If it's a more character-centric game having names with portraits is great. I also recommend an in-character quote. A pithy piece of dialogue. One of my favorite convention DMs does this. Has the players pick characters based on a card showing a picture, a quote, and the race & class, so people don't burn a ton of time looking through character sheets in detail. He also has everyone roll a d20 for pick order, again to speed things up and counteract the tendency of some players to be polite and defer and slow down the process.
*(When I last ran B/X at a convention I expected a table of 5-6 players but offered 14 pregen options; 2 of each class).