First do the grunt work of drawing the lines, getting distances/courses etc... Get your weather required for the trip, METAR/TAF/Winds Aloft/Notam's etc. Then get yourself a X-C planning sheet. There's a variety of them around, so you should find something that works for you. It should contain a "TC/MC/TH/MH/Dist/Check-points/Alt/MSA/TAS/GS/ETE/est. fuel used/est. fuel remaining" Also some bonus space is "arrival apt atis/appr/twr/ctaf/etc..." and I always had my students draw a picture of the airport with an arrow from the direction that they would be coming from. That way they could mentally picture what the airport would look like. Also we'd talk about pattern entry, taxi information if there was even taxiways' available. Also any particulars of getting fuel etc. if they need it. All the fun stuff!!!!!!! It's better to be prepared with more info than you'll ever need than to not have anything. My counter arguement to that is also that it's great to leave some things out so that the student can learn and fill in the gaps with the way that best works for them.