when people say to match the hatch how do you know what to match other than knowing what is in that lake or if you happen to catch one with something in its mouth

Both. Examine their throat to see what might be visible. Watch for chasing. Watch for subtle misses on bait to be an indication to change. We had a bait in a Baby Bass pattern that had been working great for us, and we noticed the bass coming up and swatting at it or turning off at the last second. We changed to a Smokey Shad pattern and game on. Matching what they are feeding on. This term "Match the Hatch" actually came from Fly Fishermen, who were examining the hatches on the surfaces, turning rocks over, and using small seine nets to catch larvae, etc to see what was in the streams.

We had a similar thing on Palestine this past February in a tournament. We were on fish in the grass with red trap-type baits. I caught a 17"/4# (true fatty). Since it was "SO FAT" my son started investigating it. Found a huge shad tail sticking out of its throat. He asked, "if I had any shad pattern trap baits"? I had one in a Foxy Shad. 3-4 cast later he puts a 4.5# in the boat to finish off a nearly 20# stringer.

thank you that was very informative

This may be extreme but I will throw a casting net just to grab some bait and get a closer look. I also set out a crawfish trap just to see what color the craws are in the lake�..even though this can vary in different areas of the lake.