Stop programs that launch at startup
Having your most-used applications and programs up and at 'em the minute your machine starts may be convenient, but it comes at a cost. Disable them so you're not overwhelming your elderly laptop from the get-go. To do this on a Mac open System Preferences > Users & Groups > Login Items and disable everything. Windows users: download this utility to deselect auto-start programs individually.
Offload unnecessary programs entirely
If you haven't used Final Cut since college, there's no sense in having it around just to keep your already-full hard drive company. Same goes for all of the media you've been hoarding. If you're using Spotify, Apple Music, or any other on-demand streaming service, there's no sense in hanging on to those MP3s you've been amassing since Napster's heyday. Just let go, man. But if you can't, move things onto an external hard drive.