I was reading something that said (use red for example) get a lighter red for all your lips and then outline them with a darker lip liner which makes them look bigger. Then to make big lips look smaller, do the opposite.

further to the great answer provided by @GoodFaith, be sure to use a glassy style clear lip gloss all over your lips, then dot a gloss with a pale shimmer, i.e. maybe glittery, just in the very centre of your lips. This helps to create the optical illusion of fuller lips. Also, I find using a deep red liner, just to line 'n' not to fill in, accompanied with the glossing techniques as described already, works well.

Stay away from dark shades. Go light and use gloss, gloss reflects light making them look larger. Exfoliate your lips with a baby truth brush and chapstick, this will promote circulation and bring on the plump. Apply your gloss to the middle of your lips.

You can buy some cinnamon essential oil for about $5 and massage it into your lips, and it will plump them up a little. You could also line your lips with a lipliner in the same color as your lips, and trace half way within the natural line and half over. Then take the lip liner and color in the rest of your lips. Then layer with a glossy lipstick.