You can't get rid of it afterwards, you need to do it at source. Use good quality cans that were designed to be used in the studio - Beyer DT100's are a good example. If the vocalist prefers one can off, make sure the can is not open. If you have to - tape it to his head!

Some vocalists don't need a particularly high level in the cans, get the level as low as you can without the vocalist's takes suffering. Use a second pair of cans in the control room so that you can reference exactly what the vocalist is hearing. A good can mix often reduces the need for high levels.

Don't be afraid to try things - of all things you are going to record, vocals are the most important, and the less can bleed the better. I just recently recorded a young girl who liked a high can level. One of the measures I took was to tie her scarf around her head over the cans. She looked crazy but it worked!

I second the idea of proper headsets. Closed back all the way for tracking and keep the level as low as you can. Also, it is frequently helpful to have a single ear headset on hand for singers that keep lifting one earpiece to hear themselves.

Consumer earbuds and consumer open headsets like come with ipods and cd players are unacceptable for recording use.

I'm not sure whether you are talking about headphone leakage into the microphone or a Microsoft mixer setting problem? You haven't indicated what kind of equipment you are utilizing. It's like saying Dr. I don't feel good without any specifics. If you are utilizing a cheap computer soundcard, you're not manipulating your mixer properly for the soundcard. The Microsoft mixer and other cheap soundcard mixers have both a playback & record section. A lot of people don't know this. And frequently you'll be recording what you are already listening to along with your new incoming sound. So that's a mixer adjustment not a headphone leakage problem. Unfortunately, headphone leakage is something we've all been living with since multitrack recording was born. Most of the time, it's not much of a problem or issue. It's a problem and an issue when you have open-air headphones. I have both types of headphones because open-air headphones are better for monitoring but closed back headphones are what you need to be using when you are in front of a microphone.

I like open-air headphones for their accuracy and close back headphones for cutting tracks with.
Mx. Remy Ann David

Yes, closed-back headphones are a must for tracking. I use the aforementioned Beyerdynamic DT 100's, and just ordered a couple of sets of the DT 102's which are the same headphone in a single-earcup configuration.
Also, it's often the click track that gives problems, especially in quiet passages in the music. For this I ride the fader feeding the click into the headphone and pull it down in the quiet spots. The music tracks don't cause a lot of problem because the low volume of the bleed is masked by the full volume of the music from its own track.
Jeff

thatjeffguy, post: 382807 wrote: ......Also, it's often the click track that gives problems, especially in quiet passages in the music......

Ain't that the truth! I will even mute the click if the quiet passage is really quiet.