I'm liquidating some of my stocks for a down payment on an apartment. How do I make sure my tax impact on this is as minimal as possible?

Just wondering what steps/checklists I should follow before deciding what to liquidate. I know long term gains are taxed lower so I'm planning to liquidate stocks that I've had for a while that has gained the least since only capital gains are taxed. Want to make sure I'm not missing anything.

Thanks for the advice everyone. Is there a way to easily check gains and length of stocks held on vanguard?