I bought a taotronics mhl adapter for my phone because I wanted to see pictures and videos on TV in the living room.
I have a Sensation 4G and the instructions that came with the adapter may work on the other compatible phones, but if you have a Sensation do the folllowing exactly, and in order:
First, turn off your HDTV (recommended), or at least change inputs to another port or source before beginning. (It is always recommended you turn off all components when connecting and disconnecting components to your HDTV with hdmi cables.)
Then make the hdmi cable connnections. Doesn't matter which order, tv to MHL adapter, or MHL adapter to tv.
Next make the connection to the phone. You shouldn't see anything happen on your phone yet.
(The manual says you don't need an external power source for the adapter to work, but that is not the case with the sensation.)
Next plug your charging cable into the wall first, then the MHL adapter. You should see hdmi connection made on your phone.
Now that your connections are made, turn on your tv and/or set the input to your hdmi port that is plugged into the adaptor. On your phone, your hdmi connection may disconnect for a few seconds. This is normal while the tv tries to receive the signal.
Soon you should see your phone's home screen, on your tv! You are then ready to navigate with your phone to find pics, videos, angry birds, anything you want to be displayed on your HDTV. My videos and pics looks and sound great! Make sure your media volume is up if you having problems hearing it.