Choose veggies that will grow well in the space you have. For example, planting cucumbers, peas, or beans on wall planters is a great use of vertical space.
Raised beds work well for many small garden areas. If you're using pots, make sure they have plenty of drainage and are deep enough to provide plenty of room for roots to grow.
For most vegetables, you'll want to make sure you're watering enough that the soil stays damp, but not sopping wet. Make sure all planters have large drainage holes to allow excess water to flow out.
You already have limited space, so don't let weeds take up any room! It's important to regularly look for weeds and pests to keep your garden healthy. If you're growing climbing or vining plants, make sure they have proper support as they grow.