d me walls, patios and even foundations to support my plant work.   I think the most important thing you can do is ask lots of questions.  Ask these questions of not only your own contractor but of other experts. 

Ask friends who have had similar work done to tell you about their experience.  What went right and what, most importantly went wrong.  Find out from experts what can go wrong.  For example, what if the crushed stone is not deep enough or compacted?  What will cause settling, what about cracks and water issues?   Do you need drainage build into your project?  Will the patio cause more water to flow somewhere you did not intend?

Be sure to get everything in writing from your contractor and go take a look at their work.  Seeing work that was done 2, 3 or 5 years ago is best because you can see how it weathered.

Remember an educated consumer is the best consumer!