Use those bottles
Save up plastic water or soft-drink bottles to use as mini watering systems if you're going to be away for a few days. Fill them with water, up-end and poke them into the soil beside plants.
Look to laterals
If you like to remove the laterals from your tomatoes (not everyone agrees) now's the time to start. And make sure your plants are well-staked.
Mulch like mad. But don't be tempted by all those grass clippings you're sure to have - they're not ideal so chuck them in the compost instead.
Make sure your watering system is organised for summer. If you don't have drip irrigation, check you have enough taps and hoses. Replace damaged hoses with kink-resistant ones.