Personally, I hate ladders with a passion. :) Heights are best left to birds, squirrels, etc. Having said that...
A ladder stabilizer can often help. This is a bracket that attaches to your ladder. It makes the ladder much more stable when leaned against the house. A nice thing about the ladder stabilizer is it lets you lean the ladder on the wall of your house, NOT against the edge of your gutter, possibly causing damage to the gutters.
Ladder-Max Stand-off Stabilizer
Next, make sure the ground is flat and solid under your ladder's feet. If the ground is not so, I made a wooden wedge to place under one of the feet of my ladder to make sure the ladder will be happily placed. The bottom of that wedge has spikes sticking out of it, so it will not slip on the grass. You can also buy extension ladders with one leg than can be adjusted in length to account for uneven ground.
To climb onto the roof, you want to run the top of the ladder past the roof, so it extends far enough that you can hold on when you step on and off. I'd suggest it should be at least 3 feet past the edge of your gutter, and 4 feet is better. I also have a helper hold onto the bottom of the ladder to stabilize it. A helper is a good idea in general anyway. One thing you don't wish is for the ladder to fall down when you are standing on the roof, leaving you with no way down, and nobody around to put the ladder back in position (or, as my wife might add, to call 911 when necessary.) A picture is worth a thousand words though:
Getting back onto the ladder off the roof is merely a matter of reversing your steps, as you hold onto the top end of the ladder with your hands.
Obey this setback rule: keep the base of the ladder at least 1 foot out from the house for every 3 feet in height. (Yes, many say to use a 1/4 ratio, but I often tend to go for 1/3.) So if the top of the ladder touches the house at 15 feet up, the base wants to be between 4 and 5 feet out. The trick is to not have it at too steep of a pitch, as then it would too easily tip away from the house - a bad thing especially if you are on it. The idea is that when you are standing on the ladder, you always want the center of gravity (of you plus the ladder) to be between the foot of the ladder and the house.
If I have an extension ladder standing on my deck, I'll often screw down a 2x4 cleat outside of the feet. This prevents the feet from moving/slipping out when I am on the ladder. On a grass or dirt footing, the feet of an extension ladder can swivel into what are effectively spikes that can be set firmly into the ground. These prevent the base of the ladder from moving out from under you.
Other rules - don't climb a ladder if you can avoid it when it is windy, or if you are even remotely tired or not completely focused on the matter at hand. If you are very uncomfortable with climbing ladders, money solves all problems here, as you can always hire even small jobs out.
Here are a few links you might find useful:
How to Climb a Ladder Safely
The Right Way to Set Up and Climb a Ladder
A good lube is beeswax. It lubes the screw, but does not retain moisture. I have also been known to use a stick type of teflon, used for lubing drawer guides. Or a chunk of paraffin is fine too.
You don't want to add water, so spit is a poor idea. Why encourage the screw to rust???? This is the same reason why soap works poorly. Soap is hydrophilic. Soap actually draws moisture to the screw, causing it to rust away prematurely, so a BAAAADDDDDD idea.
Drilling a pilot hole is often a help, but don't make the hole too fat, or the threads won't bite. I'll often go considerably smaller than the root diameter of the screw. Just a small pilot hole is often adequate in wood, unless one is working in a very hard wood.
Finally, if a screwdriver fails, I often resort to a brace, a hand held drill from the antique bins. Just check a hex bit into the drill and off you go. Even better, I keep my brace fitted with a quick connect for 1/4 inch hex bits always at hand.
I keep one of these tools always on the wall of my shop. It will drive a screw quickly into wood, with enough force to twist the head off most screws if I overdo it. But you also have perfect control over the torque. And the nice thing is, the battery never dies, it needs no extension cord.
Best Answer
Yes. 8 high-quality gold or stainless (not black oxide) construction screws (two at each connection point) with at least 1-1/2" penetration will hold with more than enough strength for even a typical adult.
In this case, use 3" or 3-1/2". Torx are much nicer to work with than Phillips. Pre-drill 3/4 of the screw's length and the diameter of the screw shank.