As SeaDog stated, practice.
I have two small levels, Camco #25503. Cheap, but good for what I needed.
In my driveway, got my Lexi Level using a regular carpenters level to get right on the money.
Took one Camco level and foung a place on the dash to mount it via double stick tape. This is for side to side.
Found a place on the plastic trim above the drivers door to mount the front to back level.
Now, when I pull into a spot, I can look right at the two levels and see what needs to be done.
I use the "leggo" type blocks which are 1".
After you get used to it, you'll be able to tell almost exactly how many blocks you'll need, and be able to avoid the "pull on, pull off, pull on, pull off" routine.
Steve & Cheryl + Charlie & Casey, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek
Camping trips this year so far...8