A good proportion of personal trainers are idiots. I'm not trying to sound arrogant, there are obviously good ones out there - but the title "personal trainer" does not guarantee good advice in the same sense that "chef" doesnt = good food.

There are lots of great articles on the internet if you search for them. Of course proper technique is important, but weightlifting is pretty self explanitory. Squatting, deadlifting, power cleans etc - they all require technique, but you can teach yourself.

If you want a real challenge, try to learn the Snatch - probably the best movement for developing athletic power and strength, but also one of the most challanging exercises you can try with a barbell.