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Quote:
I usually translate 's'y prendre' as 'to set about it', "to go about it", "to do it","to tackle it", or something on those lines.
These translations fit with your examples.
"la prochaine fois je m'y prendrai bien avant/bien plus tôt"
"Next time, I'll set about it well in advance"
"Tu t'y prends mal, je ne m'y prendrais pas comme ça"
"You are going about it the wrong way, I wouldn't do it like that"
I often hear it used as follows:
"Je ne sais pas comment m'y prendre"
"I don't know how to go about it / set about doing it / tackle it", etc...
Source:
http://forum.wordreference.com/showthread.php?t=302273