I never know when to stop with the level. I put the minimum at the required level for the item I'm comparing with - but how long do you typically expect an item to be useful for? I struggle to narrow it down to a selection that looks relevant to what I'm selling, so usually give up and throw it at the vendor. /poor
Well if you're buying, I don't want to see anything lower than 50 with armor, because even if the buffs are good, the armor on those items can be a show-stopper. armor matters. The exception to this rule (for me) is for when I'm searching for items that don't have armor stats (amulet, rings). It doesn't matter what level those are.
With buying weapons, I don't want to see any weapons below level 60 because I know the damage and stats I'm looking for won't be available below level 60. I also sort all weapons by dps. then by quality if I want to see quickly the highest dps Rare available.
When buying, always enter a maximum price. it will help keep your results reasonable. walk the maximum price down as you find it necessary.
Much of the same applies to selling.
If you're selling a ring or amulet, you don't sort by level. you filter based on your item's 2 *best* stats (3 if it makes sense) and then sort the results by buyout. If an item has a high tertiary stat (say 100 vit, 123 int, 93 strength), just sort by the 2 highest stats. In this example, remember people would be looking for either the 100 vit + 123 int OR the 100 vit + 93 strength, not both. so you would want to filter the results for vit and int, then do another search with the vit + strength...and note how much you think you can get for it that way.
If you're selling something with armor, I usually sort down to level 50. After taking into consideration the good stats on an item, I then look at the armor my item has vs others. If other items have similar stats but half the armor...I have an idea of where I can price mine to get it sold. I'll then sort by buy-out to see what prices items with those filtered stats are moving at and price mine based on how fast I want it to move.
If you're selling weapons...I feel like it can get kinda complicated. You have to put yourself in the shoes of a buyer and ask, "if I were at xx level, what kind of dps would I want and what stats"? That thought process can be your first filter. If you find a level 60 2h rare doing 500 damage, you really don't even need to bother trying to sell it. Nobody will want it. Level 60 items should be compared with other level 60 items almost exclusively because people at level 60 can see all of the good shit. If the damage is borderline, I'll sort down to level 58 or so. Usually, if an item is level 59 or lower, I usually filter down 10 levels, then tighten the filtering if I'm seeing too many results outside the dps range of my item. The goal of the filtering is to try to get an idea of what similar items with similar dps and stats are (1) listed for and are (2) actually selling for. With that information, you can price your item accurately and expect a sale.
Sorry for the long post, but yea. I've sold at least 60 items on the AH now. It's all about the filtering. Well, that and the time of day. It's interesting how much the price can fluctuate, but it's all based on supply & demand. sometimes you can log in and there is an abundance of an item so they're all priced competitively. other times there are only 2 of an item.