muppetgirl - I'm crocheting little halloween bags in rounds just now. All I do is;
Chain 3 (make sure you keep your first chain very loose) - this counts as first stitch working in treble (Americans call it double) crochet
Round 1; work 11 trebles into first (loose) chain, slip stitch into top chain of 1st 2-chain stitch, turn work - 12 sts
Round 2; chain 2 (first stitch), work 1 treble into base of 2 chain, work 2 trebles into each st to end, slip st into top of 2-chain, turn - 24 sts
Round 3; chain 2, 2 trebles into next st, 1 treble into next st, 2 trebles into next st (simple increase), repeat from to end, slip st to top of 2 chain, turn - 36 sts
Round 4; chain 2, 1 treble into next stitch, 2 trebles into next st, 1 treble into each of next 2 stitches, 2 trebles into next st (simple increase), repeat from to end, slip st to top of 2 chain, turn - 48 sts
Keep working in rounds, increasing number of stitches between each simple increase by one until your work is the required size (your number of stitches per round will go up by 12 each time). I find this gives a nice even flat circle & once you've mastered it you can start to have fun with chains & fancy stitches etc. Once you're finished you can close up the hole in the centre of your work by pulling on the end of your yarn & weaving it in to secure it (I prefer this method as you can close it up tight instead of being left with a hole. If you'd like to see how it looks once finished keep an eye on my blog over the next few days as I'll hopefully be adding pics of my bags soon.
p.s. - I posted this on Casbie's S n B thread but it occurred to me that you might not have gone back on it so apologies if you've already read this - I'm not stalking you honest