Does anyone have an easy way to install after market handgrips???,And how to keep them from turning loose after you do get them on?  

Grips are held on with glue so they wont' twist or slide off.  You only get one shot at putting them on right as well.  Go to Kuryakyn's website and pull up a set of their grips.  They have the install instruction on the product detail page.  

before you glue them on, take some sandpaper and rough up the grip area. then clean it off with alcohol, let dry and spread the glue around and twist the grips on to spread the glue evenly. ride safe.  

You never mentioned what bike you have.
Installing is easy........but getting the left grip to come off on a lot of cruisers is pretty much the same procedure
The right side grip usually will slide off after you have loosened the housing bolts.
The left grip is usually the one that's glued.
remove the control housing so just the grip is left on the bar.
Use a small thin screwdriver to pry the grip up a little
and spray in some WD40 to loosen the glue.......keep twisting the grip as you continually spray
after a few twists and lots of spraying the grip will just slide off. Of course you will have to clean everything before you install the new grip with glue.
Hope this helps.
Pete.  

They have the glueless grips out now . Just slide them on