I eventually found out how to make circle. I saw it at Art of Crochet - very nice and flat one. The thing is just that when you increase (by making two stitches in one "heart") you have to watch the previous round - you shouldn't increase above the place where you'd increased before. I start to increase when the centre axis of the stitch doesn't steer for the center of the circle.
I just haven't mastered finishing the rounds - I can't make the endings look all the same and be aligned in a straight line.
This is a bottom of a future pencil stand.
Tapestry crochet uses usually two threads, when only one at a time is visible. The other one is hidden inside the stitches. By changing these two you can get two-coloured crochet.
You can see that my yarn is put on the hearts (the upper part of the stitches). When you insert the hookunder a heart and bring the yarn over it, it's still placed above.
Hold the thread in its position and work with the upper one as usual. Like this you get a nice red round.
When I want to change the colours I do it at the second step. I just loop the yarn of the other colour over the hook and finish the stitch like that.
You can see that now I have a single crochet with an orange tip. This loop will be part of the next stitch. From now on you can continue with orange.
Using this technic you can crochet any picture in two colours you want. I've chosen a picture of a prehistorical hunter and his prey.
If you find a picture on the internet or draw your own, you may easily turn it into a pattern. Open it in Painting, zoom it as much as possible and press Ctrl+G (Show grid). If the picture's too big you can make it smaller by Ctrl+W (I don't know the exact names of the functions as I have the Czech version:) ).
Enjoy!