I have tried many ways including my fingers for holding components in place while they were being soldered. Recently I picked up one of my wife's hair clips and it worked great. These are inexpensive and can be found in the hair care products of most drugstore/beauty shop areas. I think I bought 10 for about $4 or close to that. See the picture for what these look like.

I searched all the hobby/technician tool sites and no one has anything that works as well as these clips.

See the picture if you don't know what I am describing.

 

When working with PTH components just simply clinching two leads works plenty well. With SMT - and NOT with the really small stuff - having two irons works well. Or holding it in place with an orange stick with one of the leads pre-tinned. Flow the pre-tinned pad with the component in place and it should hold it secure enough while you apply solder to the other side.

With SMT too small for irons, you can use solder paste. It will hold the part in place while you heat the solder with a hot air pencil or other apparatus for flowing the solder.

Many many years ago I messed with a 12 volt projection lamp with a reflector as a way of applying heat. You need to get the focal length right, but when you do you can flow tin/lead solder. Of course you'll want to wear dark sunglasses. Also found it useful for shrinking sleeving.

CAUTION: HOLDING THE HOT LAMP WITH YOUR FINGERS IS ILL-ADVISED. In other words, make a holder that can handle the heat.

 

I've used them before as alligator clips on some of the larger flat ecu pins

 

Well, they DO make decent heatsinks. For whatever you solder (or smoke).

 

Well, they DO make decent heatsinks. For whatever you solder (or smoke).

I still have some still wandering on my bench, that I bough maybe 45++ years ago, exactly for when soldering transistors to avoid excesive heat. Go figure.

 

I just use a finger to hold the component. For headers, I put a closed top shorting block on them. I can't remember ever soldering on a board that wasn't close to horizontal.