Hierarchy and balance are the central principles

I look at other logotypes to see what options look good in general - like, the mark being big, very big, caps-height, x-height, something in the middle, sitting on the baseline, above or below it, to the left, to the right, above the text, below it, have a separator line, have an enclosure, etc.

Then try it on the actual mark and type, see what works the best, then tweak by the eye. In a lot of cases the ideal composition doesn't quantify neatly, it'll be off by percentages here and there.

I usually start of with calculation. Usually in golden ratio -related factor as I'm a fan of it. But this factor may vary vastly because it all depends on type vs. symbol weight and their relation, priority and prominence.

When factor is determined I put them both together and the use optical fine-tuning of both to make it work. This is mainly relevant to those logotypes where symbol and type are somehow aligned: vertical/horizontal centre/bottom/top. Because there may as well be unaligned logotypes although rarely seen.