if this is a
RYA Yachtmaster, remember you will not be tested on Theorectical knowledge. Its doesnt really matter whether you have the YAchtmaster shorebased Cert, thats not tested.
I would reccomend you look for a 5 day on the
water exam lead in course, most schools do them, if there isnt time heres some pointers
Sail the boat like you normally do, make sure you feed the instructor properly, provision the boat adaquately as if for a 2 day sail, ensure a hot evening meal. ( dont laugh you can fail on this stuff).
The key area is
MOB under sail, and
passage planning. Usually there is a series of nav tests undereway, running fixes, sail to a place on the chart, and the infamous "BLIND NAVIGATION" test.
Underway handle the crew normally, the instructor is looking to you as a normal leisure
skipper. There is usually a night excercise, though I know sometimes it just get asked . Underway he'll usually quiz you about
safety,
weather, boat handling MOB techniques etc. He expects normally practical answers. If you seem like your remembering it from a book, hell ask you more.
Some instructors seem to focus on the COLREGS, mine didnt, never rally asked any signaificant questions on it at all.
Ensure you know your sound signals
Dave