Tower or no tower, my standard is 45 degrees to the down wind, every light on the airplane on, landing light, strobes, position, beacon.
I get a good view of the circuit and can see if there is anyone there.
At non tower anounce about 5 miles out and every time I drop my 500ft, seems to work ok.
I have noticed that a lot of airports do not seem to like overhead joins, I just avoid going it now on principle.