Some airports I’ve been to had itty bitty ladders that made it easy to get over the top of the wing and check the level of fuel.
As to passengers getting heavier…
Minimal fuel load within limits, dump any extraneous material from your flight bag, make sure you have plenty of runway. Always remember weight and balance.
Way back when airlines had scales that they had the luggage AND PASSENGERS step onto so that they knew what they were carrying.