Keep your hedges and bushes trimmed. Houses with large bushes offer cover for a burglar who breaks a window. Make it impossible to stand next to your house without being seen.
Install perimeter lighting. Make sure a burglar cannot approach an entrance in darkness. Inexpensive lights are available which detect motion. Installed on a back porch, they illuminate the area if anyone approaches.
Get to know your neighbors. The more you know about them, the more you will notice anything unusual. Establish an attitude of mutual watchfulness with them.
Report anything suspicious. You are effective eyes and ears. The police are interested in anything suspicious, whether or not a crime is being committed. If anything strikes you as suspicious (slow moving vehicles, suspicious persons, vehicles being loaded with valuables, etc) report it by calling 911. Don't worry about causing a problem. it is our job to check on these things.