Protecting your worksheet and formulas is important if you are going send other users your spreadsheet to use. Chances are they may change one of your award winning equations either on purpose or by mistake. That makes the QA of the worksheet difficult to gauge and can be a nightmare for you to unravel later.
This is a great video – the first two minutes show you some pretty cool skills on making a dummy dataset (RANDBETWEEN is a new one for me) and it is worth watching what he does here some great tips.
After this the video talks about how to lock cells on a worksheet and how to leave some cells unlocked so the user can enter data where you want them to.