Close up flower photography, macro photography, works a treat in many situations. Many flowers lend themselves very well to being "put under the microscope". But it can present many of its own challenges - very narrow depth of field and camera shake to name just two.
Narrow depth of field means only a small fraction of your flower is in focus and trying to hold the camera still to stop this 'in focus area' moving all over the place is really tricky! A tripod or mono pod can be very helpful here.
In this image you can see there is just a small band across the image that is in focus running from the drop of water on the petal on the left hand side and running diagonally across the stamens to the petals on the right hand side. It is difficult to be precise but it looks as if just 3-4mm of the image is in focus.
Knowing which part to get in focus is also important and there are various differing points of view on this. However, generally speak the central part of the flower (the yellow part in this image) usually needs to at least partially in focus otherwise the image end up "looking wrong". But, this is very subjective and the best idea is to just play around with where the focused area is and see which looks best to you. Don't be frightened to experiment!
This subject is covered in more detail elsewhere on this site - Macro Flower Photography.