It is always a good idea to remove some of the intro of a very long song and cut off the outro. Use fade in for intro and fade out for outro.
I use this mp3 converter
http://www.dbpoweramp.com/dmc.htm which is free and very easy to use.
Where posible , try not to go down below 96kbps, The sound just isn't good even thru' a pc monitors. A good bitrate to aim for is 128kbps.
Good luck and happy singin'