I'm assuming you have an HDHomerun tuner plugged into your network.
First, figure out what kind of antenna you need. AntennaWeb is a great resource for this. Provide your street address and zip code and it'll tell you how far away TV stations are from your house and which direction you need to point your antenna.
I went a little overkill and bough the DB4e antenna from Antenna's Direct.
Next, figure out how you'll mount your antenna. For me, I found a broken shower curtain rod that I used for a mounting pole in a scrap piece of lumber. I then attached the scrap piece to the joists in the attic.
Using the degree values from AntennaWeb, point your antenna in the right direction. There's a great free Compass app available in the Android store. Point the top of your phone in a direction and it'll tell you which direction in degrees you are pointing in the bottom left corner.
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Use the HDHomeRun Setup application on your computer to scan for channels. This can be found under the Digital Antenna tab. After you hit scan, you'll see all the channels your antenna can tune.
To watch a channel, click on one of the hyperlinks. If the quality is less than desired, adjust the antenna. If the antenna is far away from your computer (like mine), there's another awesome free Android app that can check signal strength: HDHomerun Signal Strength.
Hopefully, with just a couple of adjustments using the Compass and Signal Strength apps, you'll reach optimal tuning. This was a big help for me and my antenna mount in the attic. Here it is after just an hour or so of mounting and adjusting.
