currently I have a Carnelian Stone Pendant, I also have the following Citrine, rose and clear quartz,  Hematite and Selenite.

How do you know which Stone/crystal works best for you?

The clear quartz is to help you in  Meditation(connect with my spirit guide).
The Carnelian pendant I have is to help connect with the Spirit guide as well.  
The hematite is to help you with your grounding
The Selanite is to help cleanse the stone and crystal of build up negative energy.

When I went to pick/purchase them up, these stones/crystal never called out to me, When I held them in my hand, felt nothing.. I was hoping that eventually in developing my abilities these stone/crystal would come around and worki with me..

I did perform the process of cleaning and charging and program them with my intensions...  but still nothing...

I do remember one time, when meditating, I had the hematite stone in my left hand, and my clear quartz in my right hand.   Eventually both of my fists were pulsating(energy)..I wasn't cleanching hard at all..

What do you thing?
Is it because they're not a birth stone, born on May 5, 69..

How Do i know which stone works best for me?  
I would like to have a clear quartz pendant instead of my Carnelian stone, or maybe i can wear both? Will that be an issue ?

What do you think.

Personally I would say just keep trying. You are probably not attuned to your crystals or you are not sensitive to their subtle vibrations. Just hold them for a while every day and hopefully you will soon feel something :D And it's got nothing to do with the fact that they are not your birthstones...

As for the pendant issue..you can wear both as long as you feel comfortable and cleanse them regulary.

Hope that helped :D

I did noticed last night while holding the clear quartz that I did feel it's vibration... sO that's good

I'll keep working with them...

thanks