While it is not wise to base a theology on one verse, I am quoting just one because it summarises the answer to your question quite well, I think:
All that the Father gives me will come to me, and whoever comes to me I will never drive away.
The first part, "All that the Father gives me will come to me" stresses Predestination, that whoever God chooses will come to Christ.
The second part, "whoever comes to me I will never drive away" stresses Freewill: Jesus will never turn away anyone who comes to Him.
How do we reconcile these? Apparently we have to hold them in tension, like physicists who accept both the wave and particle properties of light simultaneously (physicists: this is an oversimplification and may be wrong; please forgive me - it's just an illustration :) ).
For a more detailed answer, please see How does free will fit with the doctrine of predestination?
