Best time to test OPK ?

Lena • Mom of a handsome BOY
​ladies, I have one question. As this is my second cycle off the patch and I really don't know the length of my cycles, when would it be the best time for me to start testing for O? I really want to do it right this month at least to know I've tried. 
​Another thing, I've read traveling can mess up the O during the cycles. I am traveling every week but is just a 2.30 domestic  flight and I am in a city with just 1 hr less difference. Do you think this would also influence on having late O ? Thanks