You can make a pretty decent fighting cleric without ever taking any levels of fighter, and taking levels of fighter will put you somewhat behind the power curve for spellcasting and other cool things.
However, if you do start off as a fighter I would probably do 2 levels and then switch over to cleric for the next 4 levels. After that, I'd base it on what aspect of the character I'm having the most fun with and what makes sense.
A second level fighter has some nice features such as a fighting style, second wind and action surge while you haven't sacrificed much of your clerical power yet.
I have found for my characters that I've been doing 4 levels per class so that I get the ability bonus and other features ... then again my characters rarely stay on the initial target I set for them so I may not be the best guide.