1- Specialise, and watch those races you are specialising in very closely. It is still possible to spot things that the vast majority, or most importantly the market doesn't. Various ways to specialise, hurdlers, chasers, trips, 2-y-os, all-weather etc. But have sound reasoning for choosing that particular code.
2- The seperate bank thing is good advise but following on from that, don't set unachievable targets, and try to take a long term view. Losing days and losing weeks are no big deal in the grand scheme, expect them. It's when you continue to have losing months you have an issue.
3- Don't let it become a chore, if it does, walk away and find something better to spend your time on. Remember why you first got interested into racing? Ensure the game doesn't just become about grinding out a profit. Far easier to study races with a positive outlook.
4- Leading on from what others have said, have an idea about what sort of price you expect/think a horse should be. Pricing up races is a good way of starting out this procedure. From this don't be too afraid if you price a race up and it looks nothing like the actual forecast. Remember you don't want it to be the same, otherwise there's no edge, so ensure you are pricing to what you think is their theoretical chance of winning rather than what they are likely to be. Don't waste time pricing up horses/races that you aren't confident about, but if you are specialising and doing the right work, there shouldn't be many of these races.
5- Back more winners. Everyone loves to talk about value, and the theory behind it is obviously correct, but it's winners that put bread on the table.