How to "Deny" something!

I sit and ask myself sometimes, what would be the one thing I hate about myself and want to change? I finally got the answer now... I don't know how to "deny" to something or someone. To make it more clear... This is what happens to me most of the times....

7 PM - Friday Evening...
S: Hey, you coming to temple with us tomorrow at 6 in the evening..?
Me: Yes.. It's been long time I have been there.. Let's go tomorrow...
S: Ok
Me: Deal!

9 PM - Friday
Bans: Hey, we may go to casino tomorrow. Are you coming?
Me: At what time?
Bans: In the evening..
Me: Arround...?
Bans: Not sure yaar...Somewhere late in the evening..Not coming?
Me: No..no.. I'm coming.. But just wanted to know the time..
Bans: Ah..will tell you tomorrow yaar..
Me: Okies..

11 AM - Saturday... My phone rings...
Me: Hey DC!
DC: Hey Renjana.. would you like to come with me for dance at Flannigans this evening?
Me: ***Dilemma***
***Still no second thought now!***
Yeah.. Let's go!
DC: Ok! I will pick you arround 7.30 in the evening.. We will have dinner at Coralville and then go dance at Flanningans... Is that ok for you?
Me: Yeah..sounds good!
DC: Ok..See you then.. Bye!
Me: Bye.

2 PM - Saturday!
Now I'm in dilemma having 3 plans for the evening, thinking which one to choose! This is what happens to me always! I end up not denying to anyone and half of my time in the weekend will go in thinking and deciding and then coming out of the situation... And sometimes I think about others and choose the plan what I actually didn't want to choose!

So now that I have figured out... That's not how it works... I have to work on myself and learn how to deny when someone asks me for something! At least it is better than disappointing them at the last moment!