Hello There

In response to your questions - your knitting technique may not reflect your crocheting tech. So I would recommend that you knit a guage test swatch first before you attempt your project - there is nothing so dissapointing when the project size turns out all wrong after putting in so much work.  The most common needle size I find (this also depends on the project make sure you read the pattern carefully) is 4mm for DK wool (8ply) - sorry this is Australian speak - but if you find that your test swatch is too small you are knitting too tight and need larger needles.  Best thing to do is find a really good old fashioned yarn store (you know the ones where the owner knits his/herself) to get some good advise and help.

Good Luck

Bower Bird