Tent guylines?

It varies with each different tent design, but in general you want to get the rain fly guyed out so that it is tight, and that should leave an air space of an inch or two between it and the main inner tent. That air space allows ventilation to the interior, and that is good. Having the rain fly tight on the outside keeps it from blowing around in the wind, and it tends to keep the surface more waterproof.

–B.G.–

Don't know about videos, but Bob's right on.

If the cordage is already attached to the fly, it makes total sense to stake it out just "tight enough" so it can be easily adjusted later on when the rain fly loosens up from the rain (assuming it does. Some materials will stay taught even when wet.)

Regardless, if it's somewhat windy, the extra cords tieouts will help cut down on the noise of the fly as well.

BTW, the angle you set the guylines also does make the difference and that does change also with tent design.
If you tell us what tent you are using maybe we can help.

Well I'm using an Ozark Trail (Walmart) "Ultralight" 1 person tent. Here it is:

http://www.walmart.com/ip/Ozark-Trail-Ultra-Light-Back-Packing-4-x-7-x-6-5-Tent-with-Full-Fly-Sleeps-1/40147305

Also, do I need to seam-seal or waterproof my tent. I will be camping this weekend in almost certain rain.

You only need to seal the seams that you have not previously sealed.

–B.G.–

Ok
The mid panel guylines just go straight out (at 90 degree to the fabric)
the two on the front pole I would guy them out following the same line as the pole
(looks somewhat familiar…)

according to the website this tent has taped seams, you should not need to seam seal it. Happy camping!