(This post is from a guy's point of view)
1. Think about them constantly, and let them know it (thru SMS,
email, phone call etc)
2. Perform little random acts of affection... buy a rose. Bring her
somewhere nice. Kiss her forehead on the MRT. All for no apparent
reason.
3. Be honest and truthful. It's devastating to a
relationship if one party lies to the other and is discovered.
NEVER do anything to make her lose trust in
you.... Tell her your secrets. Share your life with her.
4. Sacrifice a little of certain aspects of your life, e.g. watch
less soccer, play less computer games...so that you can spend time
with her.
5. Last but not least, tell her you love her. Often. But not so
often as to diminish its meaning... (Daily works pretty well for
me)