Trading Middle-earth cards with other players is essential if you want a decent card collection without having to pay thousands of dollars for it. However, it might sometimes be hard to determine whether a trade is fair or not. The following things should be considered when making a trade.
NOTE: These are just my thoughts on this subject – other experienced players may have different opinions.
Useful cards are worth a lot more than not-so-useful cards. For example, The One Ring is worth a lot more than Haldalam, though both are unique rare cards from the The Wizards set.
Unique rares are usually worth less than non-unique cards; players only need one copy of a unique card, but they often want three copies of a good non-unique card.
Limited edition cards (black borders) are worth more than their unlimited edition counterparts (blue borders).
The following cards from this set are worth a lot:
Assassin – excellent non-unique hazard creature
The One Ring – unique, but essential for one ring decks.
A lot of other cards from this set are quite good too (Bilbo, Mouth of Sauron, Bane of the Ithil Stone), but because ICE printed quite a lot of unlimited edition cards, and boosters and starters have been available for very cheap, most rares from The Wizards aren't really hard to get.
The Dragons & Dark Minions
These sets have also been available for very low prices, so rare cards from The Dragons and Dark Minions are usually worth about as much as somewhat useful unlimited rares from The Wizards. No cards from these sets are really valuable, but of course, some are a lot more useful than others (Many Sorrows Befall, Revealed to All Watchers, etcetera).
The Lidless Eye
Since Lidless Eye cards are much harder to find and more expensive than cards from The Wizards, The Dragons and Dark Minions, rares from this set are worth more than rares from the first three sets.
The following cards from this set are worth a lot:
A Malady Without Healing – very dangerous magic card
Chill Them With Fear – good hazard creature enhancer against minions
Elf-lord Revealed in Wrath – good hazard against minions
Heedless Revelry – very useful hazard against certain decks
Ready to his Will – allows you to turn some hazard creatures (Assassins, Slayers, etc.) into 1 MP allies
The Lidless Eye – allows you to play Sauron himself instead of a Ringwraith!
The One Ring (minion) – minion one ring decks aren't as good as hero one ring decks, but most people will want to own this card anyway
The Roving Eye – forces very nasty corruption checks
Against the Shadow
Against the Shadow boosters contain 2 rares instead of just one, so AtS rares are usually worth less than Lidless Eye rares. However, some AtS cards are R1 instead of R2; i.e. R2's are printed twice as often as R1's, so R1's are twice as rare as R2's! Don't trade R1's away unless you get something really good in return (like another R1 that's even cooler in your opinion); these cards are very probably the rarest cards in the game (some non-english promo cards excepted).
R1 cards in Against the Shadow:
Dragon factions (... Roused)*
* There are also some dragon factions in The Lidless Eye: Agburanar Roused, Scatha Roused, Scorba Roused and Smaug Roused. These are NOT R1's!
The White Hand
The White Hand boosters also contain 2 rares instead of just one. There are no R1's in this set, but there are R2's and R3's; however, the R2's are the unique ones, the R3's are the non-unique ones, so both are about equally valuable.
The Balrog is sold in two preconstructed decks, so there's no commons, uncommons or rares in this set. However, to get three copies of some non-unique cards, you'd have to buy several boxes, i.e. you only get one or two copies of these cards when you buy one of each box. These are the most valuable Balrog cards. A few examples: Longbottom Leaf, Challenge the Power, Long Grievous Siege, Maker's Map, Sauron, Desire All for Thy Belly, Unabated in Malice etc.
English promo cards used to be free (you'd send a self-addressed envelope to ICE and you'd receive a full set of promo's), right now they're a little hard to get. For trading purposes, treat them as rare cards, I'd say. In the Netherlands, english promo's are still available at tournaments.
Non-english promo's are usually worth quite a lot. Don't trade them away too quickly.
If, after reading this, you're still not sure how valuable a certain card is, check out Arco's Card Exchange <http://www.cardexchange.com> or Patrick Karcher's Site <http://www.treebeard.com/meccgtrades.html> to see how much they are asking for that particular card.
A few more thoughts:
Take your time when trading; if you're in a hurry, you might make a trade you'll regret later on.
Dare to ask advice from other people on a trade you're about to make ("do you think this is a fair deal?"). If the person you're trading with doesn't want you to ask other people's advice, he's probably ripping you off.
If someone doesn't know the card he's trading away is very valuable (an R1, for example), tell him! Never take advantage of someone's ignorance; he'll find out you ripped him off someday, and then, you'll have made an enemy.
Give newbies a break. If they desperately want a card you have, but they don't have anything you want, consider trading with them anyway, just to help them out.
If you want to start trading Middle-earth cards via the internet, be sure to visit Chris Cable's MECCG site <http://www.meccg.net/trading/>