What were the first techniques/tricks/tips you used when starting out?
So if you've read Nev's answer to this question you may have already read part of my answer.
My first real way of making gold was vendoring everything! It's amazing how grey trash items soon mount up and of course as you progress up through the levels the amount of gold you make from this increases. In part this technique requires you to loot everything possible - something that I do. I think it's good practice to loot everything as you never know what gem you might find hidden away in a pile of corpses.
However some exceptions - in the form of items that should be auctioned (if possible) as opposed to vendored. For example any cloth that you pick up and don't need. I've only recently started tailoring and have made a lot of gold from selling various cloth on the AH. Personally, I store cloth in my guild bank until it's selling reasonably well but at the end of the day anything is profit.
This brings me on to professions and specifically gathering profs. Now all profs have a means of making you money but I find the gathering profs to be the best. The individual items may not make a lot (compared with items crafted using other profs) but you will almost definately sell more. I'm sure nearly every alchemist has bought a couple of herbs, miners some ore to smelt and so on. Plus it's worth noting that whilst most professions work hand-in-hand with a gathering one (i.e. leatherworking & skinning) it doesn't mean that everyone chooses to do their own gathering and may instead buys materials.
The above three hints/tips were what I started off using and still do! They're simple and effective - what more can you want?