ah well if it's application then it's processes/code that you need to change - if it's system stuff then you need to find a quiet time. I support real 7 x 24 hour systems so things like index rebuilds are quite painful.

You can set the deadlock priority for your session ith a set command - check it out in BOL. However it doesn't stop deadlocks - just allows you to favour one session over another as the deadlock victim which is why I've never used it to date.