We have had Directv for years. SD and now HD with a slimeline SWM setup. Alignment of the HD dish is easier than the old SD antenna. The mount has scales built in for elevation and tilt.
Start with a plumb mast (very important, invest in a cheapo 1 ft level at your local hardware store). In the setup menu you are requested to enter your zip code then the receiver lists tilt, azimuth and elevation for your location. Set the antenna for the specified tilt and elevation and eyeball the azimuth (the slimline is centered on 101, same as the 18", so point the Slimline in the same direction).
If your eyeball of the azimuth is good, you will have a signal when you connect the receiver. Probably somewhere in the 80-90 range on 101. Check 103 and 99, their readings should be in the 60s. While looking at the signal meter on 103 or 99 adjust the fine adjustments for a peak signal. There is a lag between adjustment and results being seen on the meter, so make small adjustments and wait a few seconds to see your results.
The nice thing about the SWM setup is you only need one coax to the dish. We are running two HDDVR's and have a third in waiting for the belly TV. I use a smart phone app and a table to view the antenna alignment TV screen while aligning the dish. Or call inside on our cell phones.
Chris