An area of uncertainty to me is estimating distance, especially when approaching an airport. For example, if the tower at an unfamiliar airport tells me to call a 2 mi left base, I'm just really not sure what 2 miles looks like (as opposed to 1.5 miles or 3 miles). I suppose this is probably a matter of experience, but as a relatively inexperienced pilot, are there any tricks to help? I was reading a NTSB report of a MAC at my home airport (Class D, no radar at the time) which was partially due to one pilot consistently misreporting his position by a mile or sometimes more.
One thing I've done is used Google Earth to float around at pattern altitude and see what the airport looks like from certain distances, which I think does help.
The first thing you can do is get a decent road or topo map that shows your home airport (an aero. chart may not show enough detail). Note the landmarks at 1 mile, 2 miles, etc., and look for them when you're leaving/approaching the pattern. That helped me a little... I even started by plotting a normal 1/2-mile pattern on a road map, then going up to see if I was really flying that pattern when using the "halfway up the strut at 1000 AGL" method (turns out I was pretty close).
Beyond that, the only aid, beyond simple repetition, is to make a habit of using the chart (or GPS) to determine your distance from any given landmark, and just noting what the angle, etc. looks like from that altitude. Then you can play a game in cruise: as you scan, pick out something, try to guess how far away it is, then check your estimate against the chart. This is also a good way to quickly determine what the visibility is at any given point, for those moments when you are not sure if it's within limits or not.
I still find judging distance to be tricky sometimes, but these little exercises help, for sure.
Bear in mind: I am NOT recommending you be heads-down, looking at chart or GPS, while within 5 miles of an airport, to try to be accurate with your position reports. No matter how accurate your reports are, the radio will not save you from a midair- only your eyes can do that.
BUT:
As you descend from cruise to land at some new field, or even before you take off on your flight, look at the local area around the destination on the chart for a moment. Decide
beforehand where you will call 10 miles (if so inclinded), where you will call 5 miles, etc.