how to make pomegranate juice without making a mess?!

To easily remove the seeds, halve the promegranate and with a spoon tap the outer bit. The seeds should fall out very easily.

To make the juice, halve and squeeze into a jug all the juice first and then remove seeds.

PS for the 2nd answer: i think by doing that under the sink you will lose lots of juice.

Apparently the first poster has never had a pomegranate.
In a bowl of water place a halved pomegranate and with your hands scrape out the seeds under water. Most of them will quickly rise to the top.
Strain the seeds using mesh strainer.
Place the seeds in a blender and blend well.
Using a cheesecloth lined strainer, strain the juice from the seeds into a bowl. You will have fresh, seedless juice and hopefully clean clothes!
This is the way you prepare juice for making jelly.

What I do is actually mush it then put a straw into it but first you would make a hole in the pomegranate and drink the juice or even not put a straw and squeeze the juice into a cup and then drink it. It doesn't leave a mess and doesn't get on my shirt.