Bet only what you can afford. Define a bankroll at beginning of year or season and stick to it.
Define a staking system and stick to it.
Do not bet on teams or leagues that you don't know anything about. Try to specialise on chosen leagues.
Do not assume that there are any 'sure things'. Any result is possible.
Your Selection Criteria must include recent form, a minimum of last 5 matches.
In general, stick to betting on League Matches, as recent team form is only consistent within boundaries of that league.
Do not bet at beginning of season; wait until each team has played at least 6 matches so that your recent form analysis is valid.
Do not bet on local derbies or evenly balanced teams. The exception being that odds are favourable to covering your bet (i.e. cover bet with a draw).
After analysing your bets, stick by your decision. Avoid outside influences. Do not work with more than 3 Selection Criteria Strategies. Define your Selection Criteria Strategies; fine-tune them as you go.