If this has been explained already..... sorry my bad
In the past, when I have cleaned fish( not very many I must say), it was a very messy ordeal. Not too long ago, someone showed me a much more efficient and not so messy way to do this. I'll do my best to explain it in this post with pictures of the process. So here goes....
1st step. Take any of the 3 fish you see here:
2nd step. Take a pair of scissors or (hand pruners as in my case) and cut where the picture shows:
3rd step. Using a knife, slice its belly open starting from the location in this picture and continue up to where you made the 1st cut. Avoid cutting too deep to keep from cutting open its guts(less of a mess):
This is what it should look like so far:
The next step I now realize I didn't get a picture of so I'll explain it:
4th step. If you spread the belly open up near the head of the fish, you will see that the gills of both sides meet at the top side of the fish. Using your scissors or hand pruners, cut the point where they meet as far torwards the tip(nose) of the fish as you can.
5th step. Stick your finger between the body of the fish and the gills where you made the last cut with scissors and pull up and torwards the tail and the guts should come out like this:
Looking at the left side of the guts in the picture above, you can see what part to cut that I didn't get a picture of. It's the white part

and will be obvious if you try this method.
6th step. Here's the fish with the blood vein removed, just use your thumb to scrape it out:
7th step. My finished fillets. I remove the head and fins(optional).
I remove the fins because for me, the fins left on the fish are just as un-sightly as hair still attached to cooked chicken wings

:
Tight Lines,
Klocked