Most people on here don't due exact Value for Value. If that Monroe I wanted you valued at $40, and I gave you 20 Curry/Ellis cards (base, inserts, parallel, SN) and it totaled $40 but there were no GU or AU and none numbered lower than 299, does that seem fair? I mean, to some it may, you're getting 20 cards for your PC you may not have and only giving up one. But you're giving up a very low numbered card with a piece of memorabilia, a patch to boot, for everyday cards that you could possibly buy in a lot online for $10 delivered. In most cases, it's GU for GU, AU for AU, numbered for numbered (same range of numbered, not /10 for /1999), base for base, etc. When you have a combination of all three of them, then it gets closer to Value for Value.
There are people, like me, who are semi different. If I had a patch someone wanted and I valued it at $50 and they had $100 worth of base, inserts, numbered, etc. that I needed, I'd be willing to do that. Yeah, I'd like a nice Patch in return, but at the same time, I go for quantity rather than quality. Quality can be had later. My PC goal is to get as many different Pistons cards as I can. If I traded each GU for another GU, it'd take forever. But when I do trades like that, I do try to get a little bit extra in value and quantity to even it out.
Since you're a new trader, people will require you to ship first until they're comfortable with you. That could be until you have 20, 25, or even 50 trades under your belt with a high rating (above 4.75 most times). They also want to know that you are shipping your cards preferably sleeved, in top loaders, taped at the top or in a team bag, inside of a bubble mailer. But, if you HAVE to make shift, it could be not inside a top loader, but have filler cards (those nasty white things you get as decoys) on both sides to prevent damage. DO NOT SHIP IN A PWE (Plain White Envelop). If you have a printer at home, or access to one, try to ship using PayPal. It's cheaper and comes with Delivery Confirmation for tracking purposes on both ends.
Try to make sure all cards you have in your organize are rather accurately described. If you have a card that you bought in a lot that has badly dinged corners and a crease, do not mark it as NrMt, even if it's from before the 1970's. That will upset people highly and you will either have to replace the card, or send extras.
Always try to ship when you say you're going to (I've been guilty of not being able to at times). Most people are lenient, but the higher the trade, the less lenient. Also, try to make sure that you always communicate with the trader. If you had something come up at work, at home, etc, and you couldn't make it to the Post office or the Mail Box, let the user know as a comment in the trade or in a PM, or even both. This way they know that you're communicating. As soon as you lose communication, people will become suspicious and question your trading tactics. As soon as you ship, and you have a DC, provide it to the user. It won't register the same day in USPS system, but at least they'll have it ahead of time. I don't like getting a DC and receiving the cards the same day (unless it was shipped overnight).
If you can, rather than buying another box the next time you have money, try to buy a bulk lot of #000 bubble envelopes (I like Duck brand), some sleeves if you don't already have them ($50 can get you a case of 10,000 good sleeves, PM for details), top loaders if you need more, and if you don't ship via PayPal, maybe some labels that you can print out the to and from address for clarity. If you have a printer, or access to one, try and include the invoice. It shows professionalism.
Bottom line...
Treat others (and your cards) how you'd want you (and their cards) to be treated"