Good luck in you search and please call if you change your mind about professiona; I use. There are two I recommend all the time.
If you have specific concerns about anything in the home you want to buy, you may want to get a specialist in that field to look at it. If the foundation looks obvious that needs work, hire a structural engineer. Most inspectors are not licensed in any particular field so they cannot give you a 100% clear bill of health. They will tell you to "have a licensed HVAC technician look at it, or a "professional roofer" or "foundation specialist" etc...
Your new home is a big purchase and spending extra money on inspection is well worth the investment.
I would be happy to help you find an Inspector in your area if you desire. I am a Professional Real Estate Inspector and started the first, and only, working NACHI chapter in Texas. No, I am not biased towards NACHI as associations do not make the Inspector, ethics, knowledge and hard work make the Inspector.
As for associations they are a good place to start your search. You can search on the NACHI site at http://www.nachi.org, the ASHI site at http://www.ashi.org and the Texas Association Of Real Estate Inspectors at http://www.tarei.com . These are the three predominant associations here in Texas. Please keep in mind though that any association is there for the betterment of their members first. After all that is why they are collecting our dues.
There is no real silver bullet for choosing an Inspector but the number one factor should be trust. If you do not feel comfortable with the Inspector then can you really trust them? If your choice is making any claims about their abilities, et al., make sure you check them out closely. It is unfortunate in our times that so many service business' make claims that can not be substantiated.
If you have any questions you're free to call or email me. I'll try to help where I can.
Emmanuel J. Scanlan, Professional Real Estate Inspector
TREC License# 7593
Knowledge is power, but sharing knowledge brings peace!