All bobbin cases have a little metal slot which the thread goes through. If you put the bobbin in line so the thread when naturally unwinding will fall in the slot, then the bobbin will be loaded correctly. If you are unsure about whether or not the bobbin is loaded correctly, pull on the thread. The bobbin should turn in the opposite direction the thread is being pulled. It is not necessary to thread through the hole in the bobbin arm on home machines - that screws things up.
Most needles thread front to back, but in a few old machines they thread left to right.
Most machines that go L. to R. have the last few hooks go down the left side of the machine instead of the front. This is sometimes a clue that the needle front belongs on the left side. All machine needles have an obvious front and back. The front has a long thin groove going along the whole length of the shaft, the back has a short indentation near the tip around the hole. This is true even of needles that go on industrials.