If you are playing the gameplay type Capture the Flag in the Clone Wars on Marshland there are a few pointers that could help you win as the Republic.
Choose the Clone Trooper class and make a stand near the downed gunship, or by the gigantic roots that spread into the water little way from the gunship. Kill all the droids you can find, and if you are highly ranked, such as a Captain or General in medals, you can cause a diversion to allow your teammates to score, for AI infantry always go for you depending on your rank.
For defense as the Republic choose any class and stand above the root which is almost directly over the return point. Either snipe the enemy players carrying the flag, or jump down as any class EXCEPT a sniper and fire at them with your primary or secondary weapon.
Sniping from the high ground will help your fellow troopers to capture the flag.