Sending in your app before the first day of sale has never been a problem, the TO just put them on one side until the first day of sale - in fact, it was usually a good idea, as they might be nearer the top of the pile and have a greater chance of success.
My guess, and it's only a guess, is that with us being in with a shout for the title, more and more people are applying for tickets for the matches as the end of the season approaches so your chances of getting one are less as a result. Also, with the easier access to information on how to apply, i.e. on this site, .tv etc, more people now know how to apply (sorry!).
No real way to improve your chances, unfortunately, but to just keep plugging away. One thing that sometimes helps is if you are only asking for one ticket, as there's often odd seats around, though it means you are sitting by yourself - at least you're there!! That said, I know several people who got knocked back for Chelsea only asking for one ticket, so what do I know!
![Grin ;D](https://www.redandwhitekop.com/forum/Smileys/default/grin.gif)