Like everyone else here has said, I started out playing friends with plastic beakies in fairly even sets on the basement floor around books, shoeboxes, and blankets. We used WWII artillery and homemade vehicles and heavy weapons for spice. Kitbashed aircraft and toy tanks. Eventually we started buying the metal stuff, but my first group was always pretty much Marines all around. Space Wolves vs. Dark Angels and each says the other is the heretic. Eventually a friend added eldar and I added orks. We were always pretty fast and loose. Never really worried about points. And if the battle takes all day, that's fine. We even improvised rules fairly frequently. (For instance using scatter rules and for an ork dreadnought lobbing orks across a bottomless chasm the humies were counting on to keep the orks at bay. Well, some of them got across that way. And orks are pretty durable, so they were still mostly intact and able to fight after.)
Believe it or not, I actually have a tiny handful of photographs from a battle my brother and I played in the front yard. The basic scenario was a red vs. blue exercise where a mixed unit of Imperial Guard and Marines were defending a position while a larger unit of Marines attacked it. This is scanned from a print using an old Kodak Discman camera, so the resolution is not the best. I dated it 1991 on Flickr, but thinking about it, that's probably too late. I was in high school at the time, so between 1987 and 1992, but leaning toward the earlier end of that.
Defenders guarding the primary objective: an abandoned dam on a dried out riverbed. You can see a squad or two of defenders at the improvised breastworks and emplaced laser artillery in the distance, as well as a large motorized mortar. Elsewhere on the hillside are perhaps another squad of marines, a Whilwind, and a squad of Rough Riders.
The attackers muster on the opposite side of the field. Their numbers include a battalion or so of Marines, at least one Predator (and probably two, though I only see one in the picture), a Land Raider, a Spartan, and two or three squads of terminators. As well as a medivac to assist should anyone actually require real medical attention during this exercise.
Marines disembark in the face of a cavalry charge.
Mobile artillery moves to outflank the atackers.
I want to say the attackers won, but I'm no longer certain of that. It was entirely a fun game. No seriousness was anywhere to be seen. Which was . . . typical. We played fast and loose with the rules, as you can imagine. But we enjoyed building models. On at least one occasion we went so far as having a giant vehicle battle involving three scout titans and maybe a dozen tanks. Ah, floorhammer!
