There is no best way. It all depends on factors outside of the realms of these boards such as the aptitude of the person concerned, time to study, how his/her ground school runs their courses etc etc.
The only decent bit of advice on this subject is that you are better off taking as many as you can and not wasting a sitting just for the odd 1 or 2 exams. You never know you could luck out and get an easy paper even though you might be fearing the worst. Also get onto the BGS database and do as many practice papers as you can and I would be surprised if you ended up failing any in anycase. There is a reason why so many of us who have been through the torture of sitting the exams bleat on any using the database and parting with 50 quid for 3 months. It will be the best money you ever spent!