Best way to meter off camera lighting with my new setup?

So, all the components of my budget lighting setup have finally come in. With camera, my setup will now consist of:

50D
420EX Speedlite
Yongnuo speedlight
Cowboy Studio remote triggers
2 tripod stands with umbrellas
1 softbox

To this point, the only lighting experience I have is using a speedlight mounted on camera with ETTL metering, which took care of all metering for me. Assuming that I am using the full setup (both speedlights off camera, with either umbrellas or softbox), what is the best way to figure exposure? Do I need to get a light meter? Or do I just fire a few test shots and play with aperature/shutter speed/ISO/flash power settings until I get it right?

I apologize for the noob-iness of this question. Like I said, despite having been into photography for some time now, this is my first venture with any non-ETTL lighting setup.

SORRY, WRONG BOARD...thought I had clicked on the lighting board, and obviously had not. Mods, please move or delete as you see fit.

I use a regular 'ole light meter

To meter, yes you need a flashmeter. But lots of people get by with chimping (taking shots until they get the results they want). Until you get a meter I suggest this. Use your camera in whichever mode you like to meter/chimp the scene with no flash at all. This will allow you to control your ambient lighting (the part with no flash/background). Keep in mind the shutter speed needs to be within sync range. From there decide whether controlling the DOF via aperture is important to you or not. The reason I say that is you can control different aspects of the expsure using different tools based on whats most important to you. Once you pick an aperture shutter speed /iso combo that gets your base exposure where you want it. Then add the first light. Start at 1/4 power or so and take a test shot. It should be pretty apparent how far off you are that point. increase or decrease the flash power accordingly (or open or close the aperture if you wish). Once you dial in the first flash, you can make some assumptions from the power of that one, what you might want to do with the additional flash. For a 1 to 1 ratio make the settings the same, for 2 to 1 cut the power in half (assuming somewhat equal distance to subject). Its a lot easier than it sounds.