LOL is 5 vs 5 team game, so the most important thing is to help each others carefully.
In the beginning(1~11 minutes) of the game, each line have to fight with enemy in 1 vs 1, and prepare for next period. Also, there are some 2 vs 2 or 3 vs 3 matches in this time.
In the middle time(12~30 minutes) of the game, most of the lines comes to one line(Usally mid line) and fight together. In this period, there are a lot of 4 vs 4 and 5 vs 5 matches. Also, most of the games ends in this time.
Most of game ends in 30 minutes. However, there are some games that goes over 30 minutes. In this period, all players fight for hunt special monsters faster. Also, in this period, mostly there are only 5 vs 5 battle and players in each team have to support each other more carefully to be a winner.