Like a switch-click the off button.
Be honest and tell them it's over.
BrokeElectrix - distancing - yes that is exactly what i do. Or when i get an invitation from that person, i will find an excuse not to accept. I don't know if you have had those hangers-on that have no clue that is what you are doing.. trying to distance yourself and they just keep on like nothing is different. Then it calls for stronger action .. soooo ya gotta use tough love :) I'm sure you understand.
I call it "starving them out". If I am 100% sure I am done but don't want a huge blow out confrontation, I simply distance myself more and more until the relationship dies of starvation. This tends to work best when both sides are kinda over it. This barely works when the other side is actively pursuing the friendship- if you're distancing yourself and they are hanging on then the only solution might be phatnhapi's advice.
Unless you have to make an actual ceremony of ending the relationship -- i.e., calling or meeting the other party to explain why the friendship is no longer viable -- then I'd take the easy way out. Usually, just being unavailable to meet or talk over a prolonged period of time will tell the other party that you're no longer invested in the relationship. But if this is an old friendship that has been active for many years, you may not be lucky enough to do it the easy way. This means letting your former friend know that you've grown apart for whatever reasons and you wish to seek out new relationships. Not fun, but since the alternative would mean remaining in a relationship that you no longer want, your best option may be a frank discussion, come what may ...
Get someone else.
It will let go of it self with time. No calls, no letters, no nothing it just ends......The feeling of wanting to share your good moments aren't there anymore. You just forget they ever existed. Cuz you know that saying don't you. Friends come and go when God thinks you need someone He/She will put them there and when they're done he takes them away.. They are just there to make you stronger.
That's hard, if you're sure, be gentle,..thats about the only way..not sure friendships should end like that, if it really was a good one, but gentle does it if you must:)