Hi Richard -
You have both UHF and VHF-high stations to receive, so your antenna will need to cover both of those bands.
Couple of routes you could go - first, use a modest antenna like the RCA ANT751 and then amplify it if your splitters give you too weak a signal. Ideally you'd put a medium-gain amplifier on the mast, before cable losses, so that the signal is strong enough to be divided as many times as is needed.
Alternately, you could go for more antenna gain and not have to amplify the divided signal. Something like the Antennacraft HBU33 or HBU44
http://www.antennacraft.net/Antennas/AntennasHBU.html may be sufficient. Channelmaster and Winegard offer similar antennas ... just compare the specs. Or you could go bigger and put a UHF-only Antennas Direct DB4e and an Antennacraft Y5713 on the same mast and combine them with an inexpensive UVSJ combiner.
http://www.solidsignal.com/pview.asp?p=uvsj
Note that your splitters are simply voltage dividers - each divide-by-2 branch means a loss of power by 3dB. But the splitter does not add much noise, so the quality of the divided signal does not change much. You need enough amplitude at so that the resulting signal is not so weak that the tuners cannot lock on and decode.
Regarding a mast, there are lots of ways to erect a mast. The top rail from a chain link fence makes a good mast, at 10.5' long and around $10 from the home center. Usually you would exploit the configuration of your roof and building to erect the mast using one of several styles of brackets. Look here
http://www.antennapartsoutlet.com/ for various methods like telescoping masts, tripods, eave brackets, etc.