Prop portable panels at roughly your latitude: 30° to 40° across most of the US, about 50° in the UK. Add 15° in winter, subtract 15° in summer, and face them true south (true north south of the equator). That's the whole rule; the rest of this page is how to nail it at a campsite.
Plant a stick upright and mark the tip of its shadow every 15 minutes around midday. The shortest shadow points true north-south, no magnetic declination correction needed. Quicker: the sun sits due south at solar noon, roughly halfway between sunrise and sunset, so face the panel at the sun around then and you're set.
Most folding panels have three or four leg positions, so pick the notch closest to your latitude and stop worrying: a few degrees either way costs almost nothing. Panel shadows are your friend too. When the panel casts the smallest possible shadow of itself on the ground, it's square to the sun.
If you're around camp anyway, re-aim east in the morning and west in the afternoon: a fixed panel misses that sun entirely. Leaving for the day? Aim true south at your latitude angle and let it be. And keep the panel cool if you can; heat quietly taxes output, so propping it where air moves beats laying it on hot ground.
Look up the nearest town for its exact tilt and a month-by-month table, or jump straight there by zip code or UK postcode. Every city page includes today's precise angle.