What are the easiest mistakes you learned the most from when reloading?

[ar10ar15man]

anyone can post something on the internet,
be selective about who you listen to.

 

[Gwine]

Be sure to hold your powder tray under your powder measure and not your funnel.

 

[Mike 338]

I have a RCBS electronic powder scale. More than a couple times, I forgot that I left the hole open that drains the powder out of the scale. When I go to put more powder in, it dumps out all over the place as it drains out the hole in the scale.

On a progressive press, I stay away from flake powder. To many light loads that can stick a bullet in the barrel.