The best advice I can offer you is to find an inspector who is ASHI or InterNACHI certified.
Home inspectors aren't there to be easy or tough, their there to give an honest appraisal of the condition of the home. Unless you're buying new construction you should have absolutely no expectation that the home will be perfect or that you can expect the Seller to make it perfect for you, You do have every right to expect to get a structurally sound home that functions as it was designed to understanding that based on it's age not everything will be "as good as new"
I've attached a link below to a detailed article I wrote about home inspections and home inspectors. I hope you take the time to read through it as I think you'll find it extremely helpful
"Tough" brings with it the feeling of making "mountains of mole hills" or beating down a home for possible personal gains. All inspections should be fair and objective!
"Thorough" may be a more appropriate word......inspectors are licensed and bound to a code of ethics that committes them to being fair and honest. One would only hope that maintaining a high level of professionalism is something that all inspectors would adhere to.
You can always google and read reviews with regards to home inspectors. You can also check with your Agent If you are a buyer who can recommend home inspectors.
Remember, You want an inspector who can educate and guide you correctly and properly.
If you are using a Realtor to buy a home why not ask him/her for at least three recommendations.
Tough is a relative term but most agents in the business for a while know who the good ones are based on their experience.