We're not going to pretend like Republic Commando multiplayer is the greatest thing since sliced bread; there are only four gametypes, after all, none of which are particularly original. If you've played Halo 2, then you're probably not going to switch over to Republic Commando for the bulk of your online multiplayer needs. That said, the MP in RC isn't all that bad, and can definitely be enjoyable when taken on its own.
This section of the guide isn't intended to cover every single aspect of Republic Commando's multiplayer--if you've played a multiplayer game before, then you'll probably be pretty comfortable with what's offered here--but instead will consist of just what the chapter heading states: some tips.
Carrying The Flag: In CTF and Assault modes, you'll probably wind up carrying the "flag" at one point or another. As in most variants of these venerable gametypes, you aren't going to be able to use your primary weapon while carrying the flag, but you'll still be able to throw grenades, and your movement speed won't be noticeably impacted, a la Halo 2.
One thing you might not know, though, is that you can drop the flag at any time by pressing your fire button; this will let you switch back over to your primary weapon and use that on anyone who's attacking you. Of course, this isn't going to be very useful in normal CTF, where your attacker will likely run for the flag to get the quick return, but in Assault, where your enemies can't automatically return the flag to your base, you might find this useful to defend yourself or even to throw the flag towards another teammate (although there isn't much forward momentum imparted to the flag with this maneuver).
Weapon Selection: Republic Commando's multiplayer mode makes an odd executive decision by limiting each player to two weapons, besides their grenades. (If you bring up the pistol, you can switch it out for a second weapon.) You'll start each life with either the Trando SMG (if you're playing as a Trando; unlucky sods!) or the blaster rifle (if you're a commando; everyone gets one in regular Deathmatch), but you'll want to upgrade that when possible. Most of the weapons from the normal game can be found in the multiplayer maps, but there's definitely a heirarchy of usefulness here, with the ACP Array Gun (Trando shotgun) being at the bottom of the pile and the ACP Repeater and anti-armor attachment near the top. Personal preferences will come into play here, obviously, but if you want to nab a good weapon, you'll have to know where they spawn on the map and run there as soon as a round begins. You can also pick weapons up off the corpses of dead enemies, but their ammo supplies will usually be diminished, and they'll fade away shortly after their owners are killed, so be quick about it.
Making Melee Useful: If you're playing on the Xbox, then you may have noticed that it can be difficult to land a melee blow on a target that's moving quickly, thanks to the fact that your right hand is required both to aim and to press the melee attack button. We found it helpful to remap our controls so that the grenade button and melee attack buttons were switched. Throwing grenades generally doesn't require the tight precision that melee attacking will.
Super Speed: The heavier weapons in the game, such as the Wookiee Rocket Launcher and the ACP Repeater, will dramatically slow your movement speed. If you want to get a little burst of speed, and perhaps also lure enemies in by appearing weak, switch over to your blaster pistol; you'll move much faster than you normally do, even when you're using a light weapon like the blaster rifle, and enemies might think that you're an easy kill and close in, allowing you to finish them off with your super weapon when they get close.