I'm new to home brewing and want to make sure I'm using quality ingredients. I've been to a few stores, but have trouble knowing if what they offer is good quality or not. What tips / techniques can i use to be sure I'm getting the good stuff?
Well, for hops at least:
One thing to note is that for 'bittering hops' - that is, hops added early in the boil such that their bitterness is imparted, but the flavor and aroma are largely boiled off by the end, the quality doesn't matter as much as for the aroma hops.
Buy them from the store. Try making beer with them. See if the beer tastes OK. If yes, keep buying from that store. If no, find a new store.
Check the date on malt extracts. Are the cans at your store all within date or are there cans that have a decade of dust on them?
In addition, I always taste and smell each individual ingredient while adding it to the brew. Knowing what the ingredients taste like on their own will help in identifying problems, crafting recipes, etc.
Taste some of the ingredients after brewing. Spent grain? Yum! Spent hops? Maybe. Spent hot break? Ew!!!
In the long run a well trained set of senses will be your best weapons for making great beer.
The biggest piece of advice I can offer is to be sure the hops are green. This is a very easy test, even for a novice brewer, and brown hops are no good.
If you are talking about hops used for aroma/flavor (these are the hops you add toward the end of the boil), they should have a pungent aroma, like the one you want your beer to have when it is done.