What I do is put the fish in its bag into a bucket or if there is enough water in the bag I gently put the fish and water into the bucket. Then I start a siphon in a tube like this
http://www.kentmarine.com/assets/005/8758.pdf because it is easy to control the drip rate. You can also use airline tubing with a valve. Here is an article
Reefreaders - Acclimating Fish that will help and has pictures of the airline/valve setup. Over the course of an hour or more I triple the amount of water. When the water level reaches about double I remove about half so that by the end there is mostly my tank water with the fish. Here is an article
Reefreaders - Acclimating Fish that will help.
I NEVER introduce new critters directly into my display tank. I have a cheap 10 gallon tank with NO florescent lights for my
QT (quarantine tank) tank. It is kept empty on the shelf in the garage unless I have something in
QT. Here is an article on
QT.
Reefreaders - Quarantine Now!.