As a matter of course, I make it a habit to wait to call for taxi clearance until I am in view of the tower, facing the movement area, with my beacon and taxi lights on, and my engine running. If I can see the tower, more than likely they can see me. Being in a position and condition to taxi will make it easier for ATC to distinguish my plane from the others. If they still have issues distinguishing the plane, giving ATC the aircraft’s current cardinal direction heading may help.
Another good habit to make it easier for ATC (and any other pilots and personnel moving around the ramp) is to replace the country of registration designation with your plane model. Instead of saying “N”, say “Skyhawk”, “Archer”, or whatever model you are flying. According to AC 90-66B:
Paint schemes and color or style descriptions may be added to the use
of the aircraft call sign and type, but should not replace type or
call sign. For example, “MIDWEST TRAFFIC, TWIN COMMANDER FIVE ONE
ROMEO FOXTROT TEN MILES NORTHEAST” or “MIDWEST TRAFFIC, FIVE ONE ROMEO
FOXTROT TWIN COMMANDER TEN MILES NORTHEAST.
And, just because it is an airfield without ATC, doesn’t mean it is not a safe general practice to announce your movement in the movement area over CTAF.
In general, you are allowed to move the plane up to the point right before entering the movement area in the GA designated area of the airport prior to getting your clearance. Then, give ATC your position as a general landmark. If there is only one FBO, you can just say the “FBO ramp”. If the FBO has a name, use the name in place of “FBO”. If your position is at the fuel farm, say the “fuel farm ramp”. If you are at a school, use the school name. Same with a mechanic/technician shop. In place of knowing your exact position on an airport diagram, these are the places you will most frequently visit as a transient GA pilot. You can also use the closest taxiway intersection.