The more RAM you have, the better. One reason that Macs can run slowly is because apps and processes consume lots of RAM, leaving little for the others. But RAM is expensive, and adding it after you’ve bought a Mac is becoming difficult. The next best option? Minimise how much you use. Don’t keep lots of apps running if you’re not using them, and close Safari tabs. Use Activity Monitor to identify apps that are hogging your RAM and then quit them.