During the year
Tick 1099 on a vendor when you add them. That is the flag the year-end report uses, and adding it in January for the whole previous year is a day nobody enjoys.
Send them a W-9 link. They fill it in themselves and it is attached to their record — better than a PDF in an email thread, which is where W-9s go to be lost.
At year end
The 1099 report totals what you paid each flagged contractor, so you have the figures and the details in one place ready to file.
Who to flag
Broadly, US contractors and unincorporated suppliers you paid over the threshold. If you are unsure about a specific supplier, ask your accountant — the cost of flagging somebody who did not need it is nothing, and the cost of missing somebody who did is a penalty.