There's no ready-made recipe for becoming an expert on Solaris or any other UNIX systems. It's all upto you. But, here's what helped me a lot:

1. Read-Read-Read: brush up your basics
2. Get your hands dirty with the system when you get opportunity
3. Browse the troubleshooting, Q/A forums attentively; check if you already know what people are talking about. If not, get to know that.
4. Build a test environment; break things intentionally; when a man page says "CAUTION: Don't do this blah blah", just do that for fun and see what happens. Try to fix that with help of man pages (sometimes you may not be in a position to check online manuals or docs).
5. Create a file and keep a track of all the steps you have taken so far to fix a problem.
6. Learn-Learn-Learn: as technology evolves everyday, learning process never ends, so no one can say "oh yes, now I am an expert. So I gotta stop learning and start preaching"
7. "Little learning is always a dangerous thing"; so, before giving suggestions to anybody, be 100% sure about what you are saying.