The handmade projects we make contain a lot of loose wiring and are actually bad looking products. So what should I do to make my product look better and that we can actually sell directly to people? Also, we want them to look attractive when displayed in my school exhibition.
Some tips about wiring and good looking electronic prototypes / homemade devices in general:
Take a look at these images:
Image source: link
Hiding ugly PCB color under paper
Note: Don't forget that paper is flammable (thanks for Ricardo for pointing this in comments).
Image source: link
Image source: link
First, get your circuit mounted in a permanent configuration. It doesn't have to be beautiful, but it can't have connections that go intermittent because of mechanical issues. Solderless breadboards are a non-starter here, regardless of how much they helped (or hindered) you during earlier development stages. There are through-hole prototype boards, mostly with 0.1" patterns, with and without busses, that are great for through hole parts. from www.netams.com/~anton/usb-adc/08310001.jpg
If you have SMD parts, you either need to have a PCB made or you can use a board that breaks out the SMD part into a DIP mount, like shown in the photo.
Now that you know HOW BIG the prototype board will be, you can start thinking about how to box it. Any electronics shop will give you many options if you search for ENCLOSURES. Plastic is usually a better choice than metal for prototype enclosures because you don't have to worry about shorts. The board will most often mount to the enclosure using STANDOFFS.
Now, think about what the inputs and outputs are for your doohickey, including power, and think about how you're going to get those from the inside of the box to the outside of the box, and vice versa. Choose connectors. I like using 0.1" 2-row headers and ribbon cables to jump from the board to to box, so the board will be easily removable. Choosing connectors will have to do with what's available, what steps you need to take to mount on your chassis (round holes are easiest), what's right for the job (e.g., 3.5mm jacks are bad for power because they short on insertion), etc. Think about power. Do you need to include a power supply, or can you use a wall wart converter and a barrel connector? Make sure you include PROTECTION, like fuses. Think about any displays or other modes of output that you'd like. LEDs are often convenient and easily mounted with the right hardware (see pic). Think about your on/off switch and anything else you need in or on your box. Picture your user actually using it, and use this exercise to find your omissions.
Lastly, now that you've done all this and have a parts list all ready to order, take that last moment and make sure your box is still big enough when you consider all the connectors and such. Think in 3D. Your parts have height in addition to length and width. make sure your enclosure is tall enough.
Then, place your order, machine your enclosure, and build your box. Make sure you LABEL all your I/O and controls.
Here's one of my recent ones, built to NFPA99 specs for hospital safety, passed clinical engineering inspection, and (hopefully) soon to be deployed in an NICU. I still need to add labels. It uses a standard fused AC power entry module, and inside has a medical grade 5V power supply. It uses a 5-pin DIN connector to bring in an external sensor. There are illuminated buttons and paddle-type toggle switches. The LED displays are home made I2C units, and required rectangular openings in the lid, which was a pain.
You can get little aluminum die cast enclosures that look pretty good. I crammed an absolute mess of wires and boards into an enclosure I got from here and it came out alright.
I had to machine a hole in the side for a sensor and a square hole in the top for the screen to show through, but it was way easier than machining everything from scratch. This one even had a rubber gasket, so it was waterproof (not after I put holes in it of course). If you're building something with a radio in it or any kind of wireless communication, be aware that this will act like a Faraday cage and your antenna will need to be on the outside. That can actually be good though, because if you've got a bunch of FETs switching quickly or something, you won't have to worry about interference as much.