If you mean the actual sight itself, you can use a block of hard wood to support the base part, and use a brass drift and a small hammer to tap the sight out of the base.
The sight comes out from left to right, as you'd sight down the barrel.
If you don't want to do it this way, you can buy a Williams sight pusher:
http://www.brownells.com/.aspx/pid=16152/Product/FRONT_SIGHT_PUSHER
If you want the entire sight and ramp base off, this depends on how it was installed.
Most Remington rifles attach the base with two screws. One is under the sight blade.
Remove the sight blade and use a gunsmith's screwdriver bit to unscrew the two screws.
Some Remington guns attach the base with high temperature brazing alloy and removal is not easily done.
If the sight is brazed on, there are two ways to remove it.
One is to use a acetylene torch to heat the barrel to a dull red heat until the braze melts and the sight can be pushed off.
This ruins the bluing and after the excess braze is filed and polished off, the entire barrel has to be refinished.
Due to the high heat, it is possible to damage the barrel so you need to understand what you're doing and be very careful.
The second method is to cut and file the base off.
To do this, use a small hacksaw to cut off as much of the base as possible without cutting into the barrel.
With most of the base off, use files to file what's left off, then use sand cloth to polish it down to remove the last bit.
Again, this ruins the finish and the entire barrel has to be re-blued.
In both cases, since the barrel has to be re-blued, you also almost have to re-blue the receiver too, since otherwise you have to have the tooling to remove the barrel.
Bottom line, unless you absolutely have to, leave the ramp on the barrel when it's brazed on.
