Hi,
 do you have any recommendations for people who would like to create a successful game jam? I mean to attract many developers with quality games?

• What is the best time to publish jam before start?
• How long should a jam take?
• Where is the best places to advertise it?
• Any other suggestions?

Thanks in advance.

I can only answer question #2: a game jam should be generous in length, so people have time to get in a good quality entry without having to worry about the deadline. 10 days for instance (covering two weekends and the intervening work week) is a length that agrees with me as a participant. No need to make a jam much longer though, because such an event is meant for less involved games, and you can always extend the deadline for stragglers.