(Hope I posted this in the right place)
Well it's only been about a month since I started back playing Warframe after nearly a year hiatus and only playing a few hours the first time around (and therefore my knowledge is still somewhat limited), but I believe that I've learned a thing or two from doing trades, and I'd like to share that knowledge (heh, sounds a bit presumptuous, but if it helps anyone out, well I'm glad for that).
I was helped by this post that AOD_Envy made http://warframe.clanaod.net/forums/s...ad.php?t=98051 and also byt the advice given in the comments of that thread by AOD_RiverRatJr ( thank you guys for the help)
OK, i'll be going through each type of trade that I've done, and giving some tips on what I did that worked out best for me.
In terms of prime Warframe blueprints and blueprint parts, as well as prime weapons and parts, I watched the market to see what was in high demand as well as how easy or difficult it was to get said parts. I would look at what prices other people were selling at, and wait till certain times of the day (usually late evening-night-midnight) to sell for as high as possible. If after some time the parts don't sell, I would just lower the price to standard or near standard levels.
For Mods I would use the same basic formula. Most of the Mods i've sold for the most plat are Corrupted mods from Orokin Derelict Vaults. It was using the same basic formula above that I was able to sell a max ranked Frail Momentum for 100 plat.
For buying, I've found that waiting for as many people to offer you the item(s) as possible is best, that way you can go between them and haggle the price until you get a price that is as low as possible. When buying prime weapon and warframe components, I find it is best to ask for individual components and not sets, that way you are more likely to get sellers who have the single item and are willing to sell it for less, rather than a person who has more than one component and might sell the bundle for more altogether.
It was via this method that I acquired a Frost Prime set after it left the drop tables for only 150 plat.
I hope this was helpful to someone, and that the info can be used to your advantage.