WHite balance:
Read the manuals for your camera on how to do this. There should be settings to do:
White balance "hold", where you point the camera, it white balances, and then you lock it into that setting.
White balance presets- indoors, outdoors.

Ideally, you'd want to point both your cameras at a white card. A white card should fill the entire camera's frame. You then white balance there, and the cameras should be the same.
White card: A card that's white. Not all paper is white.
Where to place the white card: You should place it under the light source you are shooting at. In mixed color temperature situations, it gets a little trickier because you can only get up to one light source to appear white. You may want to angle the card so that it catches mostly the main light source.

You may find that your consumer camera may have limited white balance controls. If so, I suggest you set it on some setting other than auto-white balance. If it's on auto, white balance will shift thorough the video which would take a lot of time to correct since it's constantly changing. Some people however find that autoWB helps, because they may pan over to a different area where the color temperature of the lighting is different (if you shot with a fixed white balance, those areas would be off in terms of WB).

Color temperature: Each light source has its own color temperature, which makes some lights more orange-red and others look blue-ish. You usually don't notice this because you don't pay attention to it, and also because your eye kind of has its own auto-white balance. It constantly adjusts itself to make whites look perfectly white.
Where you have light sources of two different color temperatures, you'll see one is more oranger or bluer than the other.

*Flourescent lights have a green-ish color to them. There are sodium-vapour lights (i.e. street lights) and other lights which are weird since they emit light in specific frequencies, not over a range of frequencies like other light sources.

Zebras help you set exposure. Those diagonal white lines pop up when your video levels hit a specific level, like 70 or 90 or 100IRE.
That consumer cam may not have zebra stripes.

What you want to figure out is the correlation between the LCD/viewfinder + zebras and the exposure levels in your video. LCDs are pretty whacked in that they aren't very accurate to what your video looks like. Zebras always show up at the predefined setting, so they are consistent from camera to camera. But when you don't have them, you may need to guestimate exposure level by looking at the LCD on your consumer camera.

You also want to figure out what exposure level is optimal. Some related information on this:
http://www.glennchan.info/video/exposure/exposure.htm
If you go too high with exposure, you lose detail in the highlights. That article I wrote up doesn't really show the problem with losing detail in highlights, because the highlights on my face and on my shirt can burn out but it still looks ok. WIth other real-world imagery, you may not like that.
Too low: You lose detail in the shadows. If you bring video levels up, this can increase noise.

And as my article above points out, it seems that higher exposure levels increase the vividness and saturation of colors.

2- A lot of displays are whacked and will not show your video accurately. Generally you can forget about all computer monitors (although Vegas 6, using the windows secondary display and studio RGB mapping may be alright).
Many consumer TVs are whacked because their color temp is too high, they are too bright, contrasty, and saturated. Most can be set not to do that so they will give you an alright idea of what your video looks like.

Use Vegas 5/6's color bars generators and try the instructions at
http://www.videouniversity.com/tvbars2.htm

Hook up a TV to your deck/camcorder. On the TV, turn off auto color or flesh tone correction if you can.

If you have the money, get a broadcast monitor. They run about $600 upwards I believe.

3- Easiest way to match two cameras is to get the exact same camera, or really similar cameras (i.e. PD100 = trv900, pdx10 = trv950, vx2000=pd150, which are similar to vx2100 pd170). You still have to watch out that exposure is close... see my article above.

A cheap way to rent a second identical camera may be to hire another shooter. A lot of people own DV equipment, where paying for that person's rate is only slightly more than renting the camera.