Gather your ingredients and a bowl. I like to use the serving bowl to make the salad because then it's one less thing to wash.
Peel the cucumber and slice off the tips. Cut the cucumber in half lengthwise and then cut the strip in half again. You'll now have four long strips of cucumber. Line 'em up and whack at them with a knife... just kidding! chop them into similarly sized pieces thing 1/2 in thick. Dump them in the bowl.
Cut your avocado in half and remove the pit. Lightly, so that you don't pierce the skin, cut through the avocado and make a grid. You're basically cutting the avocado into bite sized pieces the lazy man's way. Now get a largeish spoon and scoop out the avocado meat into the salad bowl.
grab your tomatoes and chop em up into bite sized pieces. This is personal preferece really. In Greece they had large chunks I like to have smaller chunks so I can fit all the flavors in one bite.
Peel and chop your red onion into small pieces. Think minced but don't stress about it if you have a few larger chunks. Sometimes I leave these in a small bowl because the smaller pickier eaters in my family don't care for onion. Or you could chop them really small and make everyone eat it :)
Dump feta cheese into the bow. Measure with your soul.
Dump in the olives
Pour in the oil and vinegars and stir. If you want you can add in salt and pepper but I usually leave it out.
Set the bowl aside until you're ready to eat. It can be overnight or on the table. Either is fine but if the avocados sit overnight they will look slightly brown. They will taste awesome but look different.