I'm planning on installing oak or maple 3/4" solid wood floors over 3/4" OSB subfloor with a basement, but have a couple of questions regarding preparing the wood for install. I live in central Indiana.
1. Should I wait until mid-late spring to install or can I install in Feb./Mar for humidity purposes?
2. What do I need to be looking for and where are all the places I need to test for moisture content?
3. What should I use for a moisture barrier. I see some forums saying roofing paper is fine to use.

Thanks in advance for any advice and/or tips.

We install year round. The important factor is the humidity. You need a hygrometer.You'll need to establish suitable humidity levels in your house before installation - between 45 and 55%. It may not be easy with the heat going, but get as close as possible to this range. If you maintain stable RH levels year round, the flooring will behave properly. You may need a humidifier in winter months, dehumidifier in summer.

Put the flooring in the house and check moisture content in several areas of the subfloor, as well as the flooring. Figure average MC for subfloor and flooring. Flooring MC should be within 3 % of subfloor before installation.

15lb roofing felt works fine for underlayment.

Thanks for the input. I'm currently at 31% RH, and most mfg paper work says between 35% - 50%, so looks like I have to wait for a consistant warm. I run HVAC all year, so I should maintain a consistant RH year round.

Follow up questions is regarding testing for MC. Currently there is carpet on the floor where the hardwood will be getting installed. As the flooring acclaimates, does the subfloor have to be exposed during the acclaimation period. I have heard it can take weeks for wood to acclaimate and really don't want to be living on exposed subfloor for an extended period of time. Also as I'm waiting for the floor to acclaimate can I test the MC from benenth the subfloor, in the basement?

I'd demo the carpet. That way you can do repairs if need be and check flatness etc. Plus the subfloor/underlayment can equilibrate faster too.