Usually, you would want the sun at your back or at the very least not aiming directly into your lens. I wrote about this a while back and enjoyed revisiting this technique in Paris. I think that lens designers would be upset about my love for flare. They go to great lengths and expense to design lenses that resist flare and here I am trying to exploit it.
When purposely shooting for flare you are likely going to lose quite a bit of dynamic range. That’s just one of the tradeoffs, but shooting raw with modern sensors allows you to recapture much of what you think might be lost.