Place the divisor, the number you'll be dividing, outside of (and to the left of) the division bar. Put the dividend, the number that you'll be dividing into, inside (to the right of and beneath) the division bar. In order to do short division, your divisor can't have more than one digit. Sample problem: 518 4. In this case, the 4 will be outside the division bar, and the 518 inside it. In other words, determine how many times the number outside the division bar will fit into the first digit of the number inside the division bar. Write the whole number result above the division bar, and write any remainder (amount left over) in superscript beside the first digit of the dividend. In the sample problem, 4 (the divisor) goes into 5 (the first digit of the dividend) 1 time, with a remainder of 1 (5 4 = 1 r.1). Place the quotient, 1, above the long division bar. Place a small, superscript 1 beside the 5, to remind yourself that you had a remainder of 1. The 518 under the bar should now look like this: 5118. Treat the superscript number that signifies your remainder as a full-size digit, and combine it with the dividend digit immediately to its right. Determine how many times the divisor goes into this new 2-digit number, and write down whole number amount and any remainder as you did previously. In the sample problem, the number formed by the remainder and the second number of the dividend is 11. The divisor, 4, goes into 11 twice, leaving a remainder of 3 (11 4 = 2 r.3). Write the 2 above the division line (giving you 12) and the 3 as a superscript number beside the 1 in 518. The original dividend, 518, should now look like this: 51138. Keep determining how many times the divisor goes into the number formed by the next digit of the dividend and the superscript remainder immediately to its left. Once you've worked your way through all the digits in the dividend, you'll have your answer. In the sample problem, the next (and final) dividend number is 38the remainder 3 from the previous step, and the number 8 as the last term of the dividend. The divisor, 4, goes into 38 nine times with a remainder of 2 (38 4 = 9 r.2), because 4 x 9 = 36, which is 2 short of 38. Write this final remainder (2) above the division bar to complete your answer. Therefore, your final answer above the division bar is 129 r.2.
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One-sentence summary -- Use a division bar to write out the problem. Divide your divisor into the first digit of the dividend. Divide the divisor into the remainder and second dividend digit. Repeat the process until you've gone through the entire dividend.

Plastic-cutting blades have a higher tooth count than a standard wood-cutting blade. This allows for a smoother cut without having jagged edges. It also helps prevent kickback if you're using an electric saw. Ensure you're using a blade meant for cutting plastic. Use a thicker blade so the plastic does not melt and stick back together. If you are trying to cut out smaller windows in larger sheets or making small handheld crafts, use a craft blade to chip away small bits of plastic. Drill holes to use as starting points for the blade and shave away the plastic until you reach the guide lines. Clamp a piece of straight wood across the plastic with the line you intend to cut hanging slightly over the edge to cut a straight line. Guide the saw through the plastic sheet, keeping your hand on the wide portion of the saw shoe. Jigsaws allow for better mobility as you make curved cuts into the plastic. Using a blade with 10 teeth per inch, turn the plastic to make the shapes you need. Drill holes in the plastic along the guide lines so your blade has places to start and stop easily. Make straight relief cuts from the outside of the plastic to the curves. This will help prevent the plastic from warping and shortens the cutting distance. Leave room between the guide lines you've drawn and where you cut. You can always file these down later. This type of saw makes cuts only when you pull it, unlike other hand saws that cut when you push and pull it. A pull saw helps make a cleaner, smoother line in your plastic and may be easier for making shorter straight cuts than an electric saw. Use your thumb to guide the blade when you make the initial cut. From there, place the saw into the line you've made and pull the saw through.
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One-sentence summary --
Use blades meant for cutting plastic. Use a craft knife to make smaller cuts. Cut long, straight lines using a handheld circular saw and straight-edge. Create curved cuts by using a jigsaw. Make short, straight cuts using a Japanese-style pull saw.