How can I hook my tablet to my TV

I have all sort of cables and did it once, but don't remember what I did.

I hook it to the HDMI input but that doesn't work.

Ideas?

Clueless, is your TV configure to use the HDMI port? TV's will not auto-sense inputs.

Yes. I have used the HHDMI port often and can set it thru the input selection buttons on the remote and the TV itself.

I don't have a tablet but do use an HDMI cable permanently (most of the time) attached to my laptop. TV is a Samsung and I turn it on and off with the remote. I just plugged in the HDMI cable to both ends and then told my laptop which source to use for sound default. I usually leave it permanently in place because then I don't have to listen to the various bings,, bongs, bells and whistles that emanate from the computer... not to mention the never ending audio from various news outlets.
The HDMI port will eventually fail if you plug into and out of it frequently. Mine is getting loose at the laptop end and sometimes I have to wiggle it to get it working properly. I already have a USB to HDMI adapter should it finally fail.
Short version: either one or both of the HDMI female ends of your connection are faulty... or maybe the cable itself.
Adapters and cables are available at Steren's.