How to trade to NPC?

How I can trade to NPC in outdoors (not in village)?
I am choosing TRADE from TALK and very often NPC have something to trade and he show me items for sale.
Well, but what THEN?
I can't buy these items anyway - I've clicked on everything I've seen, but nothing happend! I still can't buy anything from NPC - my money haven't reduced, and I've got nothing in my inventory.
Help me!

[Wyvern]

Somebody correct me if I'm wrong on this -

To complete a trade you have to click on the NPC, not on the item it shows in the trade window.

I have managed to trade with a number of NPCs and I'm sure that it how I finally did it.

Wyv

[Davros]

Wyv,
Your back - Like Mark Twain, rumours of your d...(dissapearance to write W&W2 DWB) have been greatly exaggerated. I am in Skull castle, and just found out that if you try and swim back from the Vamp girls you get jammed in the tunel. Then if you wander back in without a scroll they get a tad peeved with you. Saw the hints section said there was another way outta here, so time to reload last save. Sure wish all my characters had Crusade chaaceristic - one very happy pixie with her double experience bonuses.

[Wyvern]

hehehehe
Davros -

Yes, I'm still around but the "other life" has been making unreasonable demands upon my time! How rude! It looks like it will continue to be demanding too but I will attempt to slip away and land here!
Yes, there is another way out of the Vamp girls lair (and why are there no Vamp guys???) After you talk to them, go through the room and out the door on the far side. YOu have a water passage, a lever and you come up in a pool near the entrance to the downstairs vault areas.

Wyv
Chaos - where brilliant dreams are born!