(adsbygoogle = window.adsbygoogle || []).push({}); Browsing around X360A and I found a few threads that could be VERY useful to ANYONE who wishes to mod their Gamerscore.
100% offline games
The quick 1000s
Tough/Long 1000s


Now, before going off and unlocking achievements, few things I would recommend.

1) If available, read the Road Map.

o Majority of the time, this will tell you how long it would take to unlock the full 1000G. It will also tell you if any achievements are glitched or not obtainable. That could save your ass from being reset.

2) Check to see whether it is available in your region or not.

Pretty stupid, but it will help. If you unlocking achievements for games that aren't available in your region, then the XBL PET will become really suspicious of your GS acquiring. Yes, a lot of people have NTSC and PAL consoles, but since Microsoftkeep their findings under wraps, it would be hard to determine how they could catch you.

3) Don't unlock too many at one time.

Personally, I unlock 250-500 Gamerscore a day. There have been a few occasions where I unlocked 1000G, but these games were offline + under 5 hours.
Set yourself a limit as to how much you should unlock. If you are adding timestamps, you still aren't safe. On average, if you are logged into LIVE 2-3 hours a day, but your timestamp shows that you have unlocked (insert GS number here) in a 12 hour gaming session, again, pretty stupid to think it, but it could raise an alarm.

4) Pre-release unlocking

You got your hands on Madden 11 (using this as an example, as it's already leaked online). What do you do? Unlock the achievements and then connect to LIVE, allowing ANY Xbox staff member to see your "achievement". More than likely, they will investigate until s*** hits the fan. Not worth losing access to your profile over 1000G a few days before someone else.
The game could have glitched achievements. Be careful.
I suppose the already mentioned 3 points apply to this as well.

5) Offline/Online (Timestamps)

Best thing to do is to find legitimate profiles via MyGamerCard and unlock according to them.

You must login or register to view this content.

If unlocking offline, obviously, times don't matter, but the order does.
If unlocking online, you could copy the exact time as the legitimate profile, or use something similar. Showing 10 achievements unlocked at 1:53am is really stupid.
Last, but not least, it's common sense. Don't expect these 5 points to get you out of trouble. You could still get reset. All it takes is one simple mistake and POOF! Your Gamerscore is back to 0, you are labelled a cheater and you can't unlock those achievements again (unless there is a way around it. I am not sure, as I am not that into modding).

I have done this to hopefully help those newbs who don't think before they act. Every detail should be looked over twice. You can never be too safe, especially when it comes to cheating the system.

If there is anything I have left out (I'm sure there is), let me know

I done 14000 in one day and I never got banned.

awesome guide man ill be sure to look at it again when my xbox arrives

I hacked my gamerscore by about 55,000 in one day, used fake dates for all of them as well. It's been about 2 weeks since I did and I still have yet to get the banhammer.