There's some subtle points you can glean by reading the old messages on this board. Like aegisx hinted, you'll have better results overall if you maintain a presence of some sort in the other system. Its easier to mine just your side, however -- just set up a cargo ship back and forth from planet with mines in cargo to the warp point.
But you'll hit the 100 mine limit sooner or later. If you catch your opponent unawares, you'll be secure. But he'll just mine his warp point to the 100 mine limit. All the while, you both work to the 100 mine sweeping capability. Then your defenses all collapse. On the other hand, your fleets are now limited to carrying enough sweeper support with them.
There's lots of dirty tricks too. Like mining in his space, where he's likely to send a ship alone. Like a ruins planet he hasn't colonization tech for yet. Or a storm system he'd hide in when in your space. Or dropping one or two mines in front of his retreat. Or even mining his side of a warp point -- just to be annoying.
