Getting tatkal ticket by IRCTC is basically depend on one thing that is completely out of our hands,I.e., Luck...But a few tips try to login around after 9:50 AM,keep all details ready which are Passenger name,ID details,don't rush and do entry mistakes if system is responding slow let it take its time don't refresh...Try it out all the best.
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BTW you can post the booked tickets PNR in PNR forum for predictions.lets see how it will progress.