When assembling something for the first time, it pays to read the instructions!
One time... yeah, one of many times, (I guess I am not always the fastest learner) I put together an all plastic bird cage. It was really futuristic looking, and the best part was the food and water cups were built into the rounded corners, so that if the bird spit his food out the side of the dish, as those miserable little creatures do (and make a mess!) the food hits the inside of the rounded corner, and it falls back into the dish. Brilliant!
So the instructions are slide/snap A into B, snap C into D, and BEFORE you insert part E into F, do XYZ!
OK, so the natural progression is to insert E into F Opps!!! Now try to get those hard plastic pieces that are snapped together, apart without braking them.
This summer I helped my nephew add a deck to his house. When he was explaining to me about how very careful measurements needed to be made to insure that one of the supports aligned properly with the lower rail of the railing. I thought that it might be easier if we just had a long drill bit and drilled right through it to mark it in place. I decided to READ THE INSTRUCTIONS! and there... plain as day we were told to lie the lower rail in place on the deck and to drill right through it.
My comment to him was along the lines of... when you have kids of your own, and have assembled enough Christmas toys, you'll have learned, that it PAYS TO READ THE INSTRUCTIONS!!!