Hi I have one of these and I know it is frustrating at first. There is quite a lot out there on the net about \'pulling a great shot\' some of it conflicting some of it intensely obsessive.
So here is one I found usefulhttp://coffeegeek.com/proreviews/detailed/pavoniprofessional/operation
I will also try to tell you what I believe will help you get going.
Number one buy decent coffee.
Like all espresso makers it the combination of grind and tamp that will lead to a good shot, this is especially true with the La Pavoni.
You must grid your own beans for this machine, or at a push if you buy from a roasting house get them to do a selection of different (fine espresso) grinds for you, mark the packs and try them all and select the best. Here in the UK coffee sold pre-ground is just to course for this machine.
So if you are grinding your own you need to experiment and every time you buy new beans you will notice you have to do it again to calibrate the grind.
A grind will be to course or the tamp to light if the coffee flows to easily and takes less than about12-15 seconds with a relativity moderate pressure on the handle again this is something you need to get a feel for. you really don\'t want to be straining to pull the shot as this means the grind is to fine or the tamp is to hard, so it is possible to have a good grind coupled with a wrong tamp.
I tend to use just two finger to pull down on the handle this way I can feel more easily how the flow is going I also have a look at the coffee coming out of the spout when you have it just right the flow kind of bends at the top rather than going straight. Also it can be quite easy to damage the machine but pulling too hard on the handle.
If you find that you are pulling down for to long and nothing or next to nothing is coming out then the grind is to fine or the tamp is to hard or both. I think in general I would try adjusting your tamp first before changing the grind.
I suggest experimentation and stick with it, it really is worth it when you start to pull great coffee shots.
Also look out for overheating the brew-head this can lead to a bad taste it can get to hot after pulling 4 or 5 shots try wrapping a damp cloth round it for a while to bring the temp back down.
So I am sorry if I have rambled on a bit but there are no hard and fast rules here.
All the best