The easiest way for me to learn was to remember the 4 elements that you use in practically every call in your career:
1) Who you are calling
At an uncontrolled field, this would be "XXX traffic", where XXX is the name of your airport. At a controlled field, it might be "XXX Ground" or "XXX Tower". If you need to call Flight Service, perhaps to open a flight plan, it would be "XXX Radio."
2) Who you are
For now, this is simply your aircraft type, followed by your N-number, without the N - "Cessna 73752", "Arrow 532PU", etc.
3) Where you are
Before you taxi, you may be "At the ramp" or "At Bravo 3" if you just landed and want to taxi in. When taking off, this may be "At runway 23" or "At runway 3R". If you are going to be landing, this may be "5 miles North" or "Over the Golf Course". When you get into flying IFR, this may be "Out of one thousand two hundred for six thousand" when you contact departure.
4) What you want to do
As simple as it sounds... at an uncontrolled field, this could be "Taking off runway XX" or "Departing the pattern to the south." If you're inbound, it could be "Inbound for full stop, runway 23." If you're taxiing, it could be "taxiing to the ramp" or "Taxiing to runway 4." On your initial call to an uncontrolled field, you will probably want to include the phrase "Request airport advisories." If you are talking to ATC, it will be stated as requests rather than as statements, such as "Ready for takeoff," "Request right turn southbound," or "Ready to taxi."
If you're flying at an uncontrolled field, you repeat the name of the facility you're calling again at the end. This is because many airports use the same CTAF (Common Traffic Advisory Frequency), so you need to clarify the airport you;re at for those who didn't catch it in the beginning. When talking to ATC, on the other hand, only one facility will be operating a given frequency, so this repitition is not neccessary.
When you put these elements together, you come out with communications that will make you sound like an old pro... "Flora Traffic, Cherokee 521 Papa Uniform is six west, inbound for full stop, request airport advisories, Flora."
Broken Down -
1) Flora Traffic
2) Cherokee 521 Papa Uniform
3) six west
4) inbound for full stop, request airport advisories
I hope this was a helpful explanation . . . Let me know if you have any questions about what I have written.