Every day in private and from the heart. Just a simple "Thank you for the gift of life" and food you have received and for just having God within you is appreciated. Go to God just to acknowledge Him and give him thanks. It's really simple, but must be sincere and from the heart.
Ephesians 6:18 (New International Version)
"And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints."
According to the bible we are to pray continually. It doesn't always have to be on our knees or formal praying. It can be little prayers while you're driving or sitting at your desk or before bedtime, etc. It's just keeping God in our minds constantly and giving Him thanks, praying for other believers (the saints), family, ourselves and the lost. It's a daily constant thing to keep us close to God. Hope that helps! :)