I've added some edits (in blue) to throw in some important points that I left out when I initially made this post.
There's no harm in getting a meter, but you can get a good read on soil moisture without one:
1. Finger test. Push your index finger straight down into the soil as far as you can, then withdraw it. Is there an indication of moisture on your finger an inch below the soil line, or two inches? An inch or less you should not need to water, but if you don't detect moisture until past 2 inches, you might need to water. The assessment of soil moisture depth, and when to water, might be different for very young seedlings or seeds trying to germinate (that is, moisture should be apparent at shallower depth).Moisture may just be a cool dampness that you can feel, does not need to be saturated.
2. "Skewer" test. You need a clean wooden skewer (like you would use on a barbecue), or chop stick, or wood dowel. Push it into the soil, leave it in place until you want to read soil moisture, then pull the skewer out of the soil. Read it in the same way as the finger test, except you look for the moisture on the skewer. Replace the skewer in the soil until you want to read again.
3. Trowel test. Insert the trowel in the soil, away from the root ball of your plants, and lift out a trowel of soil. Feel for moisture, determine from feel and appearance how deep the moisture starts.
Any soil moisture assessment, using a meter, one of the methods above, or just checking a fist full of soil, will focus your attention on the condition of the soil moisture, and is likely to improve the degree to which soil moisture is maintained.