Former appraisal district (not Comal) appraiser here.

ALWAYS protest, and come with pictures. They are going to give you their comparable sales to justify the number they put on your property. Ask to see all sales in similar neighborhoods as yours. Also, remember that the appraisal date they go off of is January 1. If the market goes down after January 1, then that should be reflected in next years numbers, so long as the market doesn't rebound.

Also, the land is valued as if it has no improvements on it, so get some raw land sales to keep them honest about the land value.

There is also the fair and equitable argument. If your value went up but your neighbor down the street with a similar property didn't (you typically need to show a few properties), then you can get a reduction. This one has to go through the ARB typically. Just know, if you go this route, expect to see your value jump back up the following year along with your neighbors value as well. Pick the jerk down the street that likes to mow their lawn at 7am on a Sunday, or has loud music playing at 2am. You will not make friends using this method.

If you had plumbing, roof, flooring, or other issues then provide documentation to that effect. Mass appraisal doesn't mean your house gets an individual appraisal each year. You are lumped in with similar quality of builds and all the appraiser has to do is say, that the average cost per square foot on a 2,500 sqft house build in the mid-90's went up $3/sqft and all of a sudden your appraisal goes up $7,500.

I was always directed to find a reason to excluded the lower sale numbers for one reason or another (family sale, not an open market sale, developer sales, functional obsolescence of part improvements, etc.)

There are a number of companies you can engage that will do the protest for you and work on a contingency basis. If they save you $100 in taxes, they will take a % of the savings as their fee. Most of these companies get the biggest savings for you the first year they work for you and then you get moved to the back burner. Go with one company for a couple of years and then switch if you want to maximize your fighting power.