I'm down at St Kilda at the moment and just stopped for a quick rest. I feel like I'm going ok in these light wind conditions. There's a slight side onshore breeze and I'm just tacking back and forth out towards a buoy and back in towards the shore again. However I seem to keep drifting further along the shore to where I set off, in the upwind direction. Tried leaning rig really far forward towards the nose of the board but it doesn't seem to be helping. What should I be looking at? I should I be putting more weight on the back or front foot to get more downwind? I admit I'm not standing back on the board so much at the moment and actually have my front foot just in front of the mast... would that make a big difference?

I had this problem a while ago and believe i posted somewhere on here but can't find it. I think the main advice given (and the advice i took) was to move my weight forward. Try sailing along and moving your weight a long way back; I found that apart from losing a lot of speed, the board will want to head upwind sharply. On my board I find i need to have my foot just behind or next to the mast base to avoid this before I start planing. I'm by no means an experienced windsurfer but I found this solved the exact same problem I had once as well.

Try moving your hands further down the boom towards the clew. This will rake the sail a little forward and drive the nose off the wind. Also, as always, look to where you want to go and have the arms extended.

The balance points on your board are a long way different between the planing configuration and the slogging configuration.
It sounds like you are under the planing speed and therefore you will need your weight forwards, (front foot heavy) and the sail angled forwards quite a bit.
As the speed increases you can shift the weight back and onto the back foot more and lean teh sail back a bit more.
In a high speed plane config, the sail is angled back and the weight is moved back to a comfortable position which is usually somewhere around equal weight on both feet.
It's something you will pick up from experience without thinking too much about it. Just move the sail and your weight around a bit until you find what works and then refine it a bit. It also varies with different boards and your weight. Some boards have a tendacy to round up wind at low speeds.

Thanks guys, I'll have a play around with where I'm standing and where I'm putting more weight next time I'm out! I probably need to move my hands back on the boom a little bit towards the clew, you're right. My mast hand is usually very close to the mast, practically in the curved section of the boom.

Don't forget to move your mast track forward as well, that will help you place your weight a bit more forward on the board.

Ah yeah, I haven't played around much with the mast track position. I've always just put it slap bang in the middle. I'll give that a shot too, thanks!

you need to use sail steering ie:lean mast forward to bear away. when going slow, then as you feel your fin start to gain effect as the speed increases you then move weight back and things get normal again.

You just need to throw overboard the little man on your shoulder saying "don't go downwind, you won't get back."

Be sure you are holding the board flat (side to side) otherwise it will be trying to carve upwind.

I had this issue a while ago when I started using a smaller fin. Moving the mast base forward 1cm helped. In the end it turned out to be a technique issue, which seems to have got sorted out after I started following Cribby's intuition tips.