Acrylic rubber stamps are the hottest new idea in stamping although they have been on the market for over a year.  If you have heard acrylic stamps stamp better by first sanding them with fine grit sandpaper do not believe it.  Even with extra fine sandpaper. You will ruin your stamps if you use sandpaper on them.   Before first use, acrylic stamps, unlike rubber stamps need to be seasoned before they will perform really well. Seasoning a stamp means to ink it up a couple times with a light ink, stamp the image and rub the ink left on the stamp all over the stamp with your finger.  This technique conditions the stamp. Using a light ink for this first stamping will help future inks stick to the stamp and reduce eventual staining. If the ink on the stamp is beading (little blobs) and is not giving the coverage you want you need to season it a couple more times.
Try not to place clear acrylic stamps in the sun. They discolor. The discoloration does not affect the stamped image but personally  I do not like the look of it.  
Buy good acrylic stamps because the cheap ones tear easily, the images do not come out clear and they do not last as long. Especially horrible with the cheap stamps is the fact they pick up dirt like a magnet. And the dirt does not come off easily even scrubbed with soap, plus it is somewhat challenging to try to clean a stamp while it's flopping around in your fingers.
Clean your acrylics after each use. The longer you let them sit with ink or paint on them, the harder they will be to clean. Use an old, soft-bristle toothbrush and gently brush them under warm water. A toothbrush is wonderful for getting into those tiny cracks.
Use a light touch when stamping with acrylics. Acrylic is more flexible than red rubber, so if you press too hard, it will smudge. Even when it is mounted on an acrylic block. As with any kind of stamp, you should not stamp on a hard surface. A couple of sheets of paper under your project, or a piece of thin foam will give your paper the cushion it needs to receive a clean image. Some stampers use a thin mouse pad.
The wonderful thing about acrylic stamps is that you can see the ink coverage of your stamp and you can place it precisely where you want it. You can double stamp easily by placing stamped images on top of each other. Tip: Before you stamp on your final project check to make sure the edges of the stamp have not picked up any ink so that you do not stamp a halo around your image. If it has, you can quickly clean it off with your finger or a cloth.
Here’s how to use your conditioned (seasoned) acrylics:  Peel the clear stamp from the plastic backing and place it on the acrylic block. Ink the stamp, position it over the paper and press down evenly for the impression. If you are using paint, cover the clear stamp with a light coat of paint using a sponge applicator and make a practice impression on a scrap paper before stamping your good project. I recommend using clear acrylic stamps as a final touch on scrapbook pages, gift tags & boxes, or patterned paper.  There are beautiful designs available with curlicues and flourishes. And the alphabets and verse stamps make precise placement very easy.                           
Did you know acrylics and other unmounted stamps can be backed with anything from magnets to static cling foam?  Many are mounted with the Halos system, which is little more then Velcro hook & loops. Some stampers prefer making their wood mounted rubber stamps into unmounteds by removing the stamp and pad from the wood mount, trimming the image close to the design and then placing it on a foam pad that sticks to acrylic blocks.
I hope this guide helps you to understand more about acrylic stamps. Happy stamping.