Know your limit.
Even the very best dubstep limiters have their limits before they cause distortion. Get to you know yours, and exactly how far you can push it with it having a detrimental effect on your master.
Flatten it out.
Timbre is important to how we perceive loudness in dubstep, so make sure a good amount of time is spent trying to achieve a flat frequency. You can do this easily by using a spectrum analyzer and finding the peaks. The best tool to cope with these is a linear phaser EQ because it will correct the frequency imbalance while also being very transparent. The first time i heard a linear phase EQ, I thought it was a joke because even cranking the effect would not have any real audible results, however that is the point of it. To give you equalization with out adding any of its own 'character' to the mix. Very cleaver dubstep tip.
Secrets of dubstep mastering.
Limiters are not the only way to create loudness, sonnox's 'inflator' is a brilliant way of giving the perception of loudness with out resorting to brick wall limiting. Distortion in small amounts can also work wonders and not forgetting multi band exciters to tickle the top and the bottom of your track to add extra sparkle and energy.
Hows your bottom end?
The bass end is vitality important to a good dubstep mix. Start from the ground up, use high pass filters on nearly all, if not all instrument tracks so the bass has its own defined space from around 100hz and bellow. To further enhance the bottom end, you might want to use a high pass filter on the whole mix, filtering out any frequencies under 22-25hz. The 'subsonic' frequencies will take up a lot of head room, and provide almost no audible gain, best to cut them out.
When processing the final 'normalize' of the dubstep master, opt for -0.1db. This will ensure you get no clipping anywhere on the track and that your hard work will not be ruined when the duplication house rejects the master for clipping reasons.
Mind the gap.
Don't cut the start of your dubstep track to the very first waveform, leave a few milliseconds so that your track is not compromised when a CD player DE-mutes or when the CD drives spins up on a digital system.
Experiment with different fade outs on your dubstep track, the standard linear fade is rarely the best option.
This should only ever be preformed once during the mastering process and is best left until last.
Use time gaps creatively.
Use the previous tracks tempo to work out when the next track should start, or using the same principal but a few milliseconds before to make the track jump out!
Although technically cheap CD's and expensive CD's will have the same quality (being a digital format, 0's and 1's cant be miss represented) the burn dye on more expensive CD-Rs will hold the data longer, and you will get a cleaner burn. You should also opt for 1x speed recording with dubstep audio to get the perfect bit for bit master. If you are using FTP to send master to duplication houses, DDP file format is the industry standard as it can't be corrupted. There is a program called 'gear pro' mastering that will convert your .wav to .ddp and it has a free trial of 30 days.
Always apply the fade after limiting and compression otherwise these processes will re-raise the volume of the fade to some degree.
Check everything your self.
Personally as soon as the track has been mastered I will put it away for a few days before re listening to it. This gives my ears a break, and you get a chance to hear it in a fresh light. Always, always listen to the entire dubstep track before production as its fairly easy for a small click or pop to go unnoticed, and once you press up your CDs you will find it impossible to be refunded for that kind of error, as it is your fault.