These are five basic points that are important to get right when sailing a dinghy. While you are sailing you should be continuously checking that all 5 are correctly adjusted for your current sailing direction relative to that of the wind.
1) Sail Trim: Use the mainsheet to keep the sail in the most efficient position. It should not be flapping (too loose) and it should not be ‘over sheeted’ (too tight). If you let the mainsheet out slowly, the first part of the sail to start flapping is the luff. If the luff is flapping then pull the mainsheet back in until it just stops flapping (and no further). This gives you the best position for the sail and a trim sail. Whilst you are sailing you should be continuously adjusting the mainsheet to be sure that it is not ‘over sheeted’ i.e. let it out a bit until the luff just begins to flap and then pull it back until it stops. If you are sailing on a beat then continuously adjust but in a different way - you keep the mainsheet tightly in and adjust by turning the boat closer to the wind until the luff begins to flap and then turning back until it stops.
2) Boat Trim: Keeping the boat, fore and aft, level. With some smaller dinghies (and this definitely includes the topper) you have to sit in different positions depending on the point of sail (sit forward on a beat, in the middle on a reach and at the stern on a run). The point of doing this is to prevent the boat dragging in the water. If the stern of the boat is low in the water and the bow is high then there is a lot of drag. If the bow is low and the stern is high there is less drag but it is very unstable at high speed. When the wind blows from behind it tends to push the front of the boat down and so it is necessary to sit well back (especially in strong winds) to stop the bow from submerging in the waves.
3) Boat Balance: Keeping the boat, starboard and port, level i.e. not letting it tip. This means leaning out (hiking) in a gust and keeping in when the wind dies (and while on a run). If you are leaning out as far as possible and the boat keeps tipping up, this is the time to let out a bit of mainsheet to ‘spill’ wind. If you want to go as fast as possible when the wind increases in strength you should throw your weight out as far as possible (using the toestraps) and then use the mainsheet to trim the boat to keep it level. This also feels very fast as your back is only just above the water and any spray squirts straight in your face.
4) Daggerboard Position: The daggerboard is needed to correct sideways drift. When the wind is blowing on the back of the boat there is no sideways drift so the daggerboard can be all the way up as it just causing drag in the water and slowing you down. When you are beating, there is a lot of sideways force on the boat causing a lot of sideways drift. Because of this the daggerboard should be all the way down on a beat to stop the sideways drift as much as possible. When the wind blows on the side of the boat there is also a lot of sideways drift, but, if the sails are correctly trimmed this is also the fastest direction. A small amount of daggerboard will provide a lot of sideways ‘grip’ in the water if it is travelling fast. Also the less daggerboard there is in the water the less drag it causes and the faster the boat goes. For these reasons the best position for the daggerboard on a reach is about half way up.
5) Course Steered: If you are sailing between 2 points A and B, you might not want to sail to point C first. Aim to sail boat smoothly in a steady direction to take the shortest route between two points. You may also need to compensate for other factors that could affect your course e.g. tide and leeway. If the tide is sweeping you sideways as you try to sail between points A and B and you simply point you boat directly at B whilst you sail, you will end up sailing in a curve. If however, you point a little up into the direction of the tide you will actually sail straight for point B. One way to check on your actual direction is to take transits. If there is a buoy at point B you may be able to line it up with something beyond (a tree on the shore or something). If this is so then as long as the buoy stays in line with the tree as you sail towards it, your course is correct. If it does not then either tide or leeway is affecting you course and you should make corrections to it.
A couple of other things worth mentioning.
Windward: The side of the boat that the wind is blowing onto
Leeward: The opposite side to the windward side
Going upwind: This means to sail the boat towards the direction of the wind. As mentioned elsewhere sailing boats cannot travel directly upwind. To move upwind you must take a zig zag course called beating. This is also called tacking, because you have to tack at the end of each leg of the zig zag.