I found something I'm not sure everyone knows about and I'd like to share!
You know how you can set the front door of a house? Apparently you can do that for the lot as a whole as well. I've been having a problem with Sims driving to a strange road to enter a lot. Well, I've got a fix for it! First, you need to turn on a cheat. Open the cheat text box by pressing Ctrl+Shift+C at the same time. Then type in this cheat: testingcheatsenabled true (to turn it off, simply change 'true' to 'false). Now, find the side of the lot you want Sims to enter from their vehicle (or by walking, whichever). Hold down the Shift key and click on the ground. Don't click in a building, you need to click on the actual ground. You'll get the option "Set Front of Lot," all you need to do is click that button. A bluish line will appear on that side of the lot and an arrow will point to where you just clicked. The arrow is where the Sims will physically walk onto the lot. You can change the location of the arrow by doing the same Shift+Click sequence on another floor tile.