I am in no way, shape, or form a professional fly tier. The pros would laugh at me, as I can tie just good enough to get by & I'm very slow at it. However, I have watched a few pro tiers & - by chance & luck - picked up a few tricks along the way. I was thinking of a few of them as I was relaxing & tying my nymphs.
One of the things I've learned is to tie up one pattern at a time. I'll tie up to a half-dozen or an even dozen of the same fly, one right after the other before I move on to a different pattern. So before I start, I make sure to get out all the tools & materials I'll need for that pattern. I keep all my tying stuff stored in a nice machinist's tool box with drawers when not in use to save space, eliminate clutter, & to keep everything organized. I'll get out only what I need for the pattern I'm about to tie. This also helps me save time, & as slow as I tie, every little bit helps.
I don't know if it's just me, but if I'm going to be tying two or more different sized flies it always seems easier for me to do the smaller size first. I know it rally shouldn't matter, but when grabbing a pinch of dubbing, or measuring wings, etc, it's easier easier for me to get the right amounts & sizes right off the bat if I go from smaller to bigger flies rather than the other way around. It is probably just how my mind works, but I've found doing it this way makes it easier on me.
Fish the same streams & hatches long enough & you'll know more of what you want to accomplish at the vise. That said, I've learned to use standard fly recipes as a guide only. The books tell you that you should proportion your flies a certain way, & that's mostly true. I think proper fly proportion is extremely important - maybe even more than color. No matter what though, you have to go by your local bugs as a guide. If that means changing the proportions slightly, or even using different materials than the recipe calls for, then do it.
The photos that follow are an example of what I'm talking about. For one of my local streams, I've learned to make the tails of my 'general' nymphs a little longer & more sparse than the flies you see in catalogs or in books. I'm using groundhog hair for the tails, as this material helps me to accomplish this. I also make the fly very 'bushy' over all. I want those hairs of the dubbing to stick out all over the place, to give the fly a lot of movement in the water, so I make them with a really hairy dubbing loop. I wouldn't just make these changes because I thought they looked better, this is what I've found better represents these local nymphs - more than a store-bought nymph would. It may not look very neat, but these changes seem to work for me as the trout sometimes agree, too.
Of course if you don't have any variations to make, or if you don't know of any you need yet, then follow the time-tested fly recipes to the letter. They've been around a very long time because they work, so respect them.
These are just some of the thoughts that pass through my brain while I tie. I hope maybe they've been of some help - or amusement - to you. Come to think of it, maybe that's why I tie so slowly: I'm busy having all these random thoughts, rather than buckling down & getting to work!!