1. Wall Location Lines. The location line is kind of an anchor point for a wall. When you flip a wall (ie. change its orientation) the wall will flip about its location line. So if you wanted to flip a wall without affecting its position you could make the wall's centerline its location line as well. Location line is controled in a wall's Instance Properties. Some of your choice settings for the location of the location line include face of core, face of finish, wall centerline, etc. When a wall is selected you might notice two blue dots at either end of the wall. Grab this blue dot and stretch the wall to any length you want. You might also notice that when you change the location line of a wall this blue dot will relocate, reflecting your newly chosen location line.
2. How do I fillet two walls (or lines). A common thing for beginners, is to go right to the trim tool in search of a fillet option (because they are likely more familiar with AutoCAD). Well in Revit the fillet tool is located elsewhere. If you are drawing a wall or a line there is a pallet of line shapes that you can draw (square, polygon, circle, arc, etc.) Well fillet is one of those options circled below.
3. Stretching a gridline in the current view only. When working with gridlines for the first time a beginner will often take notice that stretching the end bubble of a gridline stretches the grid in all views globally. The next question they ask is, "How can I stretch it for this view only?" Well there is a little icon next to a grid bubble that reads "3D." Click on the icon and you'll notice that it now reads "2D." You are now free to strech the gridline for the current view only. The location of the original 3D grid bubble is at the hollow circle you see below.
4. How do I host my railing on a ramp or stair?: Ok, so you've sketch a new ramp or stair and you want to add a railing to it, but the railing is resting on the first floor and doesn't slope with your ramp or stair. Well, when you're in sketch mode shaping your new railing path, there is a tool called "Set Railing Host." Select this tool and then select your host (stair or ramp). Your railing will now slope with the host as was your original intention. Remember, the railing tool is located on the Home tab and is its own sketch. Do not try editing the sketch of your stair or ramp to add new railings. I've seen beginners try this alot.
More beginner tips to come...