#1 is dust.
#2 could be hair or it could be stress on the film that fractured the emulsion. (e.g. bending the film.)
#3 looks like a combination of #1 and #2.
#4 and #5 are out of focus but they could be hairs.
Everything looks like it was dust, dirt or damage that was on the film at the time it was shot or developed.
Keeping your cameras clean it key to preventing this kind of thing. Keep your developing equipment clean, too.
Canned air can help keep the dust off lenses and out of the film gate but don't forget that canned air only blows the dirt up into the air where it will settle back onto something else.
You will clean the lens you are working on but everything else in the room will eventually get dirty. Take the item you are working on into another room, outside or somewhere the dust doesn't matter.
Also, if you are blowing dust out of a camera, BE CAREFUL! That air can cause damage to fragile parts like shutters and focusing screens.
Not only can the force of the air blow parts out of line, the stream of air can accelerate dirt particles to supersonic speeds which will then "sandblast" anything else they come into contact with.
Use, carefully aimed, short bursts of air and be mindful of the "dust cloud" you are creating and you'll be all right.
Past that, you just have to be meticulous about dust and dirt in every stage of your work. It takes experience to be able to "see" the dust before it shows up on your film and in your final prints.
My only other advice is to learn how to spot.
