I was looking at the Tamiya instruction sheet for my M4 Sherman. It looks like the stars are on the left side of the hull but not the right. Is this correct or were they placed on both sides (there's enough decals for both)? Also, there are a couple of decals with letters and numbers on them (unit markings?), are these every specific? What I'm getting at here is that I'd like to do a solid olive drab paint scheme with segmented stars, but the the instruction sheet shows the segmented stars only on camo jobs. I know with aircraft the serial numbers and markings are all very specific. You can get "historically incorrect" real easy. Is this true for armor also?

TIA...Kevin

Unfortunetly, yes. Vehicle numers on armor can include everything from Divisional, Battalion, Unit, Company, etc.
As far as what decals are given in Tamiya's kits to represent a specific vehicle are as often incorrect as they are correct.
Your best bet is to find some actual photos of the vehicle you are building and use what decals you have to represent it. Many Shermans in combat photos don't even have their numbers displayed anywhere! Some even have no stars. This could be from several factors. From whitewashes to repaints to wear and tear. Heck, some units even removed the stars all together. They made good targets for German gunners.
Unless you are going for a specific vehicle from a specific battalion in a specific time period, I wouldn't concern myself too much with it. That does not mean you have free range and can just put any numbers anywhere. That would lead to inaccuracies.

Kevin, you can go to this page for examples of Shermans with very few marking on them. :

http://www.military.cz/panzer/indsk/m4sk.htm

Ooops, I forgot to mention one thing. Tamiya's decals are notoriously too thick. If you have no others, than by all means use them. If you have an option, toss em and use another manufacturer's.
If you use Tamiya's, try to cut them as close to the actuall decal as possible,(trim off any unnecessary borders). Other wise you could see the film after it's applied. Use a setting solution like Solvaset, to help them "seat" to the model.

Solvaset is suerb. I spray dull coat on the model, then soak the decal, let them sit on a tissues then place a small amount of Solvaset on the place spot. Slip the decal onto the area, pat it gently down with the tissue, then apply a little more Solvaset around the edges. Great stuff. I appreciate the point about the Tamiya decals. Their national emblem stars always have a slight border that is impossible to get rid of. Cut those babies close and you will diminish the problem.
DJ