Help on signing free agents please?

I'm new to this horsetrading stuff, can u guys help me? My questions are:

1. Can anyone explain the cap room and why the value is in negative? Is it being negative a good or bad thing?
2. What does the % in Change for? is it an incentive for players to sign up with me?
3. I'm having a hard time signing players to multi-year contracts. Any tips on how to entice players to sign up?

Thanks in advance

1. This thread contains some explanations of the salary cap

2. You can set yearly amounts on the contract to either increase or decrease each year, allowing you to save a bit of cap space now or down the road while still signing a player.

3. The easiest way remains to give them exactly what they want, or just slightly more than what they're asking.

When re-signing free agents ive found that they wont budge on the amount of years they want to re-sign for, but they will accept less than the amount their asking for most of the time, say its Ray Allen wanting 70mil over 6 years you can probably sign him for 68mil or so, its not huge but it can make a difference.

When signing other teams free agents they rarely accept less than what they're asking

As far as getting under the cap goes its all about getting your star players contracts ending at the same time, having some young talent rising up from the draft and hoping decent players test the free agent market!

I couldn't ever sign a FA to more than +/- 1 year over his preferred length. Even changing 1 year costs me and arm & a leg over his preferred salary.

I don't think being negative cap affects your GM rating in any way, i've still get high ratings going high over cap. It limits your choices since you can only sign FAs for min, but if your major players are in place, it's not too bad.