I have a recipe I want to try. It doesn't say to sift the flour. Should I sift or not sift? 

There can be as much as a 1/4 cup of extra flour in 1 cup of unsifted flour.  It never hurts to sift.

I usually whisk the top of the flour a little and measure with a spoon from there rather than fully sift and measure — just kinda fluff it up a bit — certainly some recipes are designed around the no sifting —

i mean we’re not supposed to cram the measure down into the flour container and scrape it full — that’s where kakeladi says we’d get way too much flour — and of course you haven’t said that either — but some recipes ain’t ‘sposed  ta be sifted — but fluffy flour is what I aim for on the times I don’t outright sift

I usually only sift cake flour because it's always lumpy. If I'm using AP flour, I'll whisk it with the other dry ingredients and that's usually fine. 

Yup, I’m a “spoon and level” then whisk kinda gal...but mostly because I’m too lazy to get my sifter down :).

I sift when the recipe calls for it because as kakeladi said - you can end up with way more flour than intended if you don't fluff up that compacted flour. I scoop or spoon it into my measuring cup and level off with a knife. I sift when there are spices or cocoa added to the flour. Whisking before measuring does fluff the flour up and get rid of lumps.

My older recipes call for sifted flour so I sift for those ones. I have 3 sifters - all different sizes so hey - I cannot have them taking up valuable real estate in my kitchen cupboards unless they are being used...lol. ( Heavens , I also have sieve strainers of different sizes).

I notice most people these days don't bother though. 

I'm probabl;y like the person K8 mentioned:  when I fill my storage container I want to get the whole bag of flour into it so I pack it in :)  I never thought of just whisking it.  Sounds like a plan :)

Yes @rychevamp same here.

I've converted all my recipes to weights (pounds, ounces, or grams) so there is never a worry about compacted flour.

When I have a recipe where I'm adding lots of dry ground spices to the recipe, I put the spices in a bowl with the flour, salt, baking powder, baking soda etc. and gently whisk it all until I can see that the spices are well blended & disbursed. 

I weigh my flour using 128g per cup of APF or 112G per cup of cake flour no matter what the recipe says. 

If I'm subbing cake flour for APF or vice versa. I still use the weight of whatever the recipe was written for... if a recipe calls for 3 cups of cake flour, I'd use 336g of flour even if I were using APF, which would actually be 2 5/8 cups.

After weighing my flour, l whisk in the leaveners & salt (spices and cocoa, too), then sift them together, whisk, and then sift again.

Most often, I do as -K8memphis described, fluff up the flour, then spoon it into the measuring cut and level.  For a few recipes, I do sift and I always like to sift cake mixes when doing a WASC version.  They always seem to be sort of lumpy.

All of my recipes are in weight as well.  If I try a new recipe, it gets converted as I make it. I can't stand measuring cups. Too many extra things to wash, and too many variations in weight so who knows what you'll end up with. It's just way more accurate and a lot easier to multiply the recipe.

One of my main cakes has sifted cake flour. So, I sift it, weigh it, add the leaveners, then sift again. It makes a difference in the texture of the cake. But, then one of the chocolate cakes I make, doesn't matter if it's sifted or not, it will still lump