Don't be discouraged if you hit a 'losing run.
' This happens to all of us occasionally, and the winners will more than compensate for these losers in the fullness of time.
The Rules for Common Sense Betting

1. NEVER bet in races with more than eight runners or less than four.
   With eight runners in a race there are enough to make the odds competitive without risking too much opposition to your selection.
   If you bet in nine or ten horse races, you are merely increasing the chances of your selection being beaten.
   Why give it more opposition? Also a race with just seven or eight runners allows the jockeys to obtain a suitable position in the race, and there is less bumping and jostling in small fields.
   In short, a field of this size is usually `true` and the best horse usually wins.
   The minimum of four runners rule is to avoid `false` races where pace is often difficult to judge.
   
2. NEVER bet in handicaps.
   Horses running in handicaps are weighted to finish in a line - in theory.
   It is usually very difficult to predict the outcome of such races.
   
3. NEVER bet when the going is soft, or heavy.
   This type of going can make a mockery of the form-book.
   

If you use the above three rules to select your races for the day, this will give you the best chance of making a profit from your bets.
In these races you can either make your own judgments and selections or use a newspaper tipster of your choice.
By incorporating the three simple rules above you will be using a common sense approach to your betting and give yourself the best chance of finding plenty of good odds winners.
Give it a go.