I probably look at my Hornady Manual first most of the time.
Second would be my Lyman Manuals, I have the Lyman 49 as well as the Lyman Pistol & Revolver Manual.
Next choice would be my Sierra Manual, that I have added a few sheets of my own to.
I have the newest Lee, but I do not reference it much at all.
I have the 3d and 5th Nosler Manuals that I do not use much either. Load date all seems to be on the very conservative side, and only covers bullets they sell.
I also have an old Accurate arms manual. Only covers Accurate powder.
I also have Ken Waters Pet Loads.
I also use the Quick Loads computer program to get an idea how things should work. You can change barrel lengths, and work with all sorts of bullet and powder combinations. I really like this resource. I do normally cross check what I come up with with a second source.
Then we have loading data available from web sites. I use them a great deal also.
Any data that looks on the warm side I like to cross check with a second source.
Then you have the other side of the coin, some loading data has been watered down way to much over the years The 38 Special comes to mind. Down loading the 38 Special is probably a result of all the OLD guns, and Airweights that could be damaged by a diet of warmer ammo.
OR no one has took the time to work up new loads in the last 25 years with current bullets and powders. The 264 Magnum comes to mind.
Lots of good information in this post. Looks like the majority would go with Hornady or Lyman for a First, then start adding more. I am in this same camp.
A thought: You have a computer or you would not be posting.
Make up a Data Sheet on your computer. Set it up as a fill in the blanks File Card for Powder, Charge Weight, Bullet Used, Primers, Seating Depth, Velocity, Test Gun Information, Notes: etc. Work out the card size to fit in a File Card Box. Print your cards on Card Stock, and you have a record of what you have loaded. Keep a record of success and failure.
Another option is to make up the Cards, and fill in the Blanks with a Pen and add them to your Card Box as you work up a new load.
Bob