Best approach in the early days is just to have sex three times a week, every week! I don't set too much store by ovulation apps/calendars, they assume you'll ovulate around halfway through your cycle. A period of OPKs and charting (and later my pregnancy dating scan) suggested I ovulated more like CD11 in a 27 average cycle - apps suggested CD14/15. If I'd relied on the app I'd used exclusively, I wouldn't have got pregnant!
Look for other signs like EWCM (cervical fluid that looks like egg white), possible ovulation pain and a general desire to do the deed as well!