You can check current prices and market history via the summoning bell.

[zakalw3]

Yes, lots of people know this, but I'm surprised at the amount if people I find daily who insist you have to run from bell to board to review prices.

If you didn't know: while in your retainer menu, put an item up for sale or adjust a currently selling item's price, and click the icon in the top right to bring up the market board page for that item.

[Tarta]

Oh really? Then this gave me learning this day. Thank you!

[Jonno]

Holy crap this is awesome. Thanks for the tip.

[zakalw3]

Bumping, because people need to know if they don't.

[Shaone]

Yes this is a nice feature. I hope soon we can buy from those listings too.. for those situations where someone has listed a few items at npc / 1 gil, and you want to grab them and add them to your own listing

Another retainer management tip is picking "Sell Items from Retainer", then opening your inventory. This way you can sell items from your own inventory, retainers inventory and transfer items between the two, all without switching back to a different menu option.

[Feyniphia]

Wow, awesome tip Zak! Thanks!

[Tupsi]

Yep, sadly it doesn't stop...a certain "kind" of people from constantly undercutting items into oblivion.

[Dschlitz]

This explains some of the ridiculous prices on some items (low and high). Like Tupsi said above, it won't stop undercutting unfortunately.

[SevenHeavens]

wow I didn't know this

thank you

[Felis]

Another tip:
The default price in the selling UI is the price you would get from selling it to a NPC, not the price it is worth in the AH.