It took me 3 tries to get a grow to completion
Watch how it grows when you get one there (or close) and watch what get's big, what doesn't. Not just buds , but stems. Look at where they come off the plant and how that effects them.
For the most part, the first 2 nodes that pop shoots out are losers. You don't have to snip them early, but they will almost always be smaller than the next node's sprouts/limbs.
If you are doing a scrog, every shoot is going to get light and make a decent flower, but it is still going to be random sizes based on where it came off each individual stem.
Pruning the lower stuff off a little at a time as it grows is usually safe. On each shoot/limb that you want to keep and turn into a big bud, just keep 3-4 nodes growing on the top to feed the plant. All the growth is going to center on those areas. The fewer there are, the bigger the stems and flowers.
Once you flip and see pistils, you can see better what will produce and what won't. You can also see what grows after the flip (about the first month) and keep getting rid of lower stuff on each stem that will be smaller, but eat stuff the top would have eaten.
It really doesn't matter as much in veg, as long as you don't take too much and keep in mind what you want for a finished product (what shoots to keep, where to top, LST, etc.) it will keep growing.
In flower I leave as many fan leaves as possible, because there won't be many more. I get real selective, and they usually have to be shading something for me to prune them. Big lower fan leaves are also a good barometer for the health of the plant. They will show most issues first before it hits the rest of the plant.
Hope this helps. This is just how I do it and why. Many other methods and reasons. Waiting to hear other's replies.