Whether the paint job is outside or in, masking is almost always needed at some stage. Unless the section to be painted is nowhere near a surface you don't want touched, this preparation step will be vital.
Nothing looks more unprofessional than globs or streaks of paint where it doesn't belong.
For quick and cheap masking efforts standard ivory masking tape is good enough. It got the name for a reason. But for sections where the plastic covering or tape will remain in place for more than a day, blue tape can be a big time saver.
Blue tape, also known as safe release tape, has a special adhesive that clings well but comes off cleanly. After a day in the sun and air, ordinary crepe tape will split and ooze. That leaves glue and pieces of masking tape on the surface when it's removed. That makes for a much more difficult clean up. Blue tape doesn't have that drawback.
Blue tape also is safer to use on a variety of finishes. Scraping or even washing off ordinary masking or crepe tape opens up the possibility of ruining the surface that the tape covered. That partly defeats the purpose of applying it in the first place.
Some do-it-yourselfers will try to cut expenses by using newspaper. That may be fine for very small jobs. But for any extensive effort, using newspaper will have undesirable drawbacks. Newspaper readily gets wet, whether from paint or water. That leads to too-easy tearing, making the covering useless.
There is an alternative that still uses paper. Specialized paper designed for house paint masking jobs is flexible and sturdy. It sheds water and holds up well to paint drips. But it can be a little on the pricey side and may or may not be reusable, depending on the treatment it gets.
Plastic, especially tarps or covers that are made specifically for paint jobs, is often the best bet. Cheap plastic, such as a large trash bag, isn't designed to have the tensile strength or other properties needed for good masking. Using plastic covers (which often come in large rolls) made for the job yield the best result. Frequently, it can be re-used.
Spending a few extra dollars for good paper or plastic covering is worthwhile.
Applying plastic covers and taping it off requires no special skill, just patience and care. Take the time to be exact and be willing to use more than you think you need. It isn't fun, but the better you prepare, the better the final results.
Apply a strip or area of tape to any exposed outlets (after removing the covers) to keep paint from getting inside. Ditto for light switches. Not only does dried paint make it difficult or impossible to use the outlet or switch, it can cause electrical problems, such as providing insulation where it shouldn't be.
Apply tape in long strips onto the plastic, leaving an inch or so of adhesive exposed. Then apply the mask to window sills, door frames and anywhere else they need to go. Inspect the area carefully to ensure that nothing is visible that isn't supposed to get painted.
Now for the easy part. Painting.