if you are in a part that has multiple bodies you can hid the individual bodies. just go to the feature tree and there is a folder up the top "bodies" expand that and right click on the bodies you want to hide. you can select multiple bodies at once or all bodies by holding shit and or ctrl and clicking on them. you can show them again by repeating the above process but click the "show" icon. hovering over the icons will show you what they each do.
alternately you can hide the individual features by left clicking on them and clicking on the little glasses icon in the tool bar that pops up. if you are working on a single body part doing this to one feature will turn everything off. you can turn it back on by clicking on any of the features and clicking the glasses again.
you can left click and click the icon that looks like a yellow cube above a grey cube with a down arrow beside them. this will suppress the feature. depending on the feature you suppress this may automaticlly suppress other features that are dependent on that one you have suppressed. these should un-suppress when you un-suppress the original feature. if they don't just un-suppress them manually. to un-suppress something left click and click the icon that looks like a yellow box over a grey one with the up arrow beside it.
if you are in an assembly
you can turn the visibility of the other parts and assemblies in the same manner as mentioned above.
the same with suppressing parts and assemblies. just be aware that when suppressing things in an assembly where they are mated to each other will potentially cause your feature tree to light up red and yellow with unsolved mates. it will also mean that the remaining items are free to move again if not constrained properly. but that will be shown by a ( - ) symbol beside the feature tree name. this will fix itself when you unsuppress the items again. and you shouldn't be able to move parts about when editing a sketch anyway. so no big deal.
alternately when in assemblies you can select the things you want to work on and right click and select "Isolate" from the menu. when you are done editing you can click "exit isolate" from the dialog box that appears when you isolate things and everything will go back to normal. this is a much easire and nicer alternative to suppressing things. the save button in that same dialog will allow you to save the "isolation" as a "display state" which you can then return to at any time without having to select the parts and isolate them again. another nice feature of this method. if you want to access display states you can go to the third tab along in the top of the feature tree and they are down the bottom of the panel.
hope this helps.