Ask him if Nargles use his nose as a ski ramp

Buy him a shampoo and conditioner set. In pink sparkly bottles.

When he talks on and on about how Dumbledore trusts him, shout BROMANCE!

Recommend him Snarry fanfic.

Read him out some of the more *intimate* chapters of Snarry fanfic during quiet Potions classes. Put large emphasis on certain phrases. When he tries to stop you, simply raise the volume.

Tell him how much you loved his diary. When he asks what you're talking about, show him Snape's Diary on youtube.

Wear an "I love James and Sirius" t-shirt. All the time!

Buy him an apron saying "Kiss the Cook."

When his cloak billows as he walks, shout the Batman theme tune: "Dunna nunna nunna nunna Batman!"

Buy him eye-brightening eyeshadow. If he complains, tell him how "It'll really light up those dark tunnels in your eyes."