Whats the best thing to do for a tent that is leaking rain through the seams?

There are lots of different types of seam sealers available. I’d use one of those.

Watch the weather report,...

something like this

I put Thompson water seal on old tent one time. It worked for a while but sure did stink.

Also, if you are sitting in a tent while it’s raining, don’t touch the fabric. The water will typically follow the fabric to the ground by capillary action. If you touch it, now it’s going to drip in the tent where you disrupted the flow. Drip, drip, drip all nigh long where you just had to put your booger picker on the roof.

I have had great luck with the star bright water proofing stuff on my tents.

Do they still sell tents