(Of course, I had to get that in there. Anyways, ...) Get yourself a copy of the Installation Instructions. A 'set' comes with each box of flooring. If you can get to the store in advance of the install, have them rip open a box and make you a copy.
In general, 3/4" solid stripping is recommended to be installed over 3/4" plywood. If it's OSB or particle board, an underlayment is recommended. A Tongue-and-Groove sub-floor is fine too. If the sub-floor is 1/2" or 5/8", a double-layer is recommended.
Again, the best way to know what should be done is to get the Instructions. If the MFGR. has a WEB site, it may be posted there. Call the MFGR and have them e-mail a set to you if you can't get to the store. My best to ya and hope this helps.