well mate... if your fishing over rough ground ( rock ) your best bet is to change to a grip lead. i know this sounds odd but it will stop your rig rolling into the holes where a snag is enevitable.
if your fishing over heavy kelp then its worth changing tackle to somthing that can handle it. a Daiwa SL20SH/30SH would cope perfectly loaded with 30lb line this would just rip the kelp from the bed.....!!
The perrenial problem! I'm definitely NOT AN EXPERT but we all get snagged at times so there's not necessarily anything wrong per se. However..... yes you could be really unlucky and be casting, every time, into a snag fest of a piece of ground. (take the advice offered earlier and try to get down at Spring Lowto find the snags (and lost leads!) Always remembering that fish are after food and this tends to congregate in snaggy, kelpy, rocky places because it wants somewhere to hide!
I bet that what you might be doing is casting out and then reeling in lots of line before you get settled. This is giving your end tackle plenty of opportunity to find somewhere nice to get stuck! Cast out, stop your reel when the weight hits water, then allow just a little free spin to reach bottom (at first don't even do this perhaps) Then just tighten gradually (in really snaggy places I do this with the rod on the rest) Yes a grip lead works better because it 'anchors' your tackle straightaway. Don't keep reeling in or you'll spring the wires prematurely! Thus the first time you start to reel in will be because of a bite or because you want to re-bait. Don't shilly shally, bring it in briskly with your rod tip up as high as you can get it. You can use a 'lead-lift' which is like a 'wing' on your lead which lifts the lot off the bottom quickly as long as you're reeling in briskly. Some anglers who fish the rough regularly, swear by the SLOSH because of its rapid retrieve (like some of the new BIG fixed spools). I just swear (a lot) when I forget and let the weight fall back after a missed bite. An anchored rig is a 'BOLT' rig (to use a coarse fishing term) the fish picks up the bait and feels resistance so bolts in panic. Thus it hooks itself. How often do we see the fish 'biting' when it's already hooked! (I offerred this advice last night on another thread about grip or not grip!)