For now there aren't a lot of tips. I just periodically check the pc to make sure it's all going smooth, but I guess if you refresh periodically there's no point.
Just make sure you use the best browser for your pc(intel- firefox, amd-chrome I think) and minimize the browser(I've checked and I get better hashes this way).
With the current global hash rate around 3Mh/s, the chance is to get one block per day with an average pc of 1500hash power. If you have some bad luck you might be getting nothing for days, as the block/day is just an average estimation(you could get nothing for days then get 2-3 blocks a day).
Your estimate is quite optimistic. With such an increased hash rate I'm not getting any blocks for many days now, so I had to stop mining. The comparison that was made a few posts ago with bitcoin is getting more and more accurate: just like it makes no sense bitcoin solo mining, now the same begins to be true for webdollar.