That the single best improvement that you can make to your 336, 1894, 1895 etc is to remove the sloppy factory trigger and replace it with a Wild West Trigger Happy trigger kit.
I have always thought that a good trigger was the first step in the making of an accurate rifle. I have 4 Marlins and they all wear the WW trigger! For $85(my cost at Brownells) you can turn a good rifle into a great rifle!
I will have to admit that the last one I installed took a lot less time to install than the first one! However if I can do it anyone can!