Hi Sunshine.
It depends what you are trying to do.
For chopping veggies etc. try speed 4-5, stopping every few seconds to check until you reach the desired consistency.
Mixing really depends on what is in the TMX. A cake mix may take anywhere between speed 4 for a smaller more fluid consistancy mix, up to speed 7ish for a fuller bowl with a thicker consistancy. BUT if you want to mix without cutting then use a slower speed and the Reverse
function.
Creaming sugar and butter I'd use speed 4.
In your cook book you should have a "Guide To Basic Functions) which also comes as a fridge magnet for easy reference.
Hope that helps a bit.
