Micro Greens
Soil Based Systems:
Most microgreens prefer a room temperature of about 70° F…give or take.  As you select your microgreens, your supplier should have this information along with other growing tips to consider.  Some micros like Cilantro, prefer soil temps a bit cooler.  Use a heat mat if your ambient temperatures are going to be too low
They are grown in a medium like soil or a hydroponic grow pad and are usually grown and harvested at about 10 days, which is usually 7 or 8 days past the sprout stage. They are grown in trays and can be grown right on your kitchen counter-top or outdoors on a porch or patio

In most cases, especially municipal water sources, your water will be too high in pH.  Use a pH test kit that will test from pH 4 – pH 8 (at least).  Ideal pH of microgreen water is about 6.0.  Most municipal water systems will have a pH around 7.0.  A good guide when using lemon juice to acidify, is 2 teaspoons of lemon juice per gallon of water
Soil Method:

•Pour 1-2 inches of soil into a tray without holes (you can use a tray with holes if you use one without holes as a drip tray). Moisten with water and gently pat it flat. The soil should be firm but not compacted.
•Evenly spread seed over soil surface. The more seeds on the soil, the denser the crop will be.

Gently pat the seeds to make sure they are making contact with the soil, but do not crush them in.
•Thoroughly mist seeds with a spray bottle. Cover with another tray and place in an area at room temperature.
•Uncover and mist seeds 1-2 times per day. Remove cover permanently when you can see the sprouts have taken root. Expose to light and continue watering as needed.
•When the first leaves appear, start tasting your microgreens every day to mark the changes in flavor as your crop matures.
•Time to harvest may vary between seed varieties. When the flavor is to your liking, it's time to harvest! All you need is a sharp set of scissors that can cut as close to the growing media as possible.

With some greens, you can just pull them out of the media and trim off the roots and seeds at the base.  You should lay out the greens and pick out any remaining seeds and shake off any soil or other impurities.
 

Hydroponic Method:
 
Hydroponic mat
blend of biopolymers and natural fibers is designed to manage water efficiently for optimal growth in a variety of hydroponic systems
Most pads are not re-useable.  Microgreen roots occupy every square inch of these pads and so after harvest, and drying them out, they either fall apart, or they’re compacted and don’t absorb water like they did when they were new.  Reusing pads also asks for root and seed diseases that can effect the next crop.
Most people would recommend to always water from underneath. For a couple of reasons, one is you don't want your not microgreens to be falling over into the soil and getting stuck there because that prolonged contact with the soil will allow the stem to weaken due to being moist which will allow infection in and then your tray will start to die.
Your medium will determine a lot of that if you're using you know coconut coir or soil or hemp pads or rock wool you know the frequency with which you water
•Pour 1 cup of water into the bottom of a tray without holes. Place the hydroponic mat in the tray and allow it to soak up the water.
3% food grade mist to prevent mold
•Evenly spread 2-3 tbs. of seed over the mat. The more seeds on the mat, the denser your crop will be. Try to keep the seeds from bunching together.
•Thoroughly mist seeds with a spray bottle. Cover with another tray and place in an area at room temperature.
•Uncover and mist the seeds 1-2 times per day. When the sprouts have taken root, remove the tray permanetly and expose to light. Continue watering as needed.
•When the first leaves appear, start tasting your microgreens every day to mark the changes in flavor as your crop matures.
•Time to harvest may vary between seed varieties. When the flavor is to your liking, it's time to harvest! Gently trim microgreens just above the roots.