I’m diving into KiCad for the first time and have drafted a schematic. Could someone please review it and suggest any necessary changes or improvements? I’m eager to learn and enhance my design skills. Any feedback on potential mistakes or areas for improvement would be greatly appreciated. Thank you in advance for your guidance!
I like adding big fat titles to identify sections, but try to keep the titles short, as they take up a lot of space. You don’t need to add “connections” to each title. You also do not have to add titles to each and every little section.
I find adding rectangles around sections contra productive. It makes the schematic look messy and it is a nuisance to maintain. A bit of whitespace around sections is a lot cleaner.
Each project also needs to find a compromise between using labels and drawing wires. Drawing boxes around all those sections, also implicitly prohibits using wires to connect things, and this is also a bad thing.
I like to have things ‘connected’ 
so my schematics looks differently (intentionally details not readable):
But how your schematic looks to be easy readable for you - your choice.
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I personally do like to box things off however use them sparingly. As an example I have 3 sections to a headphone amp design, Left and right amplifier stages, power supply and filtering and inputs and outputs and I agree with @paulvdh make the titles short and sweet not so ‘in your face’ Dotted lines can look ok too, also in the case of your ‘sensors’ box I would have connected the device to the connector with labels not wires. At the end of the day is it readable and contain all the info that it needs to and are you proud of your work !
I also have a (reverse engineered) schematic of a headphone amplifier. It’s from an beyerdynamic A1 clone kit from Aliexpress, and I have put it in a hierarchical design, because it has two channels. So on the main sheet there is just a power section (on the bottom) and a startup delay (on the right) (I think it also does overvoltage / clipping protection).
I also had to put the input connector, and potentiometer in the upper left corner just next to the hierarchical blocks.
Note that I did not bother to put big captions on this schematic. It’s just too straightforward and easy to read.
Zooming in on the upper left section:
And the hierarchical sheet with the actual amplifier:
(Yes, there is a total of 6 voltage regulators on this board).
Also note I have used very little labels. Things are mostly drawn in place and connected with wires. I have also adhered to the common rule of "voltages go from top to bottom, and signals go from left to right). This makes the schematic easier to read and it reduces the chances of for example connecting electrolytic capacitors in reverse.
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Now you just need to change the hierachical sheet outputs to, well, outputs.
I think you should look at lots of schematics and learn to assess them critically to come up with a style that works for you.
Not to mince words, but I hate the style you have posted, which unfortunately has many practitioners. It’s no better than a visual list of components and wires. I prefer my schematics to “tell a story” about how the signal flows. Some wiring by labels is unavoidable. Buses can help reduce clutter.
But there are worse sins than this block style. Inverted GND and VCC rails. Wires that zigzag every which way.
Neatness is not just visually desirable. Bad drawings make it harder to mentally analyse the circuit and can obscure errors.
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We’re on the same page. A spreadsheet would be about just as useful. But like you say, it seems to be in fashion.
@Shubham_Tiwari, here’s an example of my style, where signal flows are obvious and function partitioning is done using hierachical sheets:
AVS.pdf (610.2 KB)
I’m with @retiredfeline and @ML9104
I like to see a story; like a book.
You have two development boards. Where is the beginning?
You have unconnected PPMs on the left of both. Are the modules joined? Are they substitutes for each other or are they supposed to be joined?
You have A1, U1 & U3. Where is U2? Is it on another sheet?
U1 is connected to J7 sockets. Where is the other half of J7, the plugs? On another sheet?
To what do J1, J3, J4, J5 & J6 attach? I see pins but no sockets. Where is J2? Is it on another sheet?
You only have groups of four wires making most of the connections, so draw them. It is not worth bothering with busses.
If your story starts with the Black Pill, mirror it on the Y axis so you have four wires connected to the Arduino.
Drop another four wires to the mosfets and also attach the J plug pins to the mosfets.
Run two wires from the Black Pill to U3.
Remove all the blue text and boxes.
Pay attention to your symbol numbering.
Create the other halves of all your J symbols and add motor symbols to the appropriate connectors.
Add connecting wires or explanations to the other half of the J7 connector.
Making the above changes will make the schematic self explanatory and save the reader having to ask the dumb questions I had to, at the beginning of my comment. 
This is rough sketch of how I would present your circuit. It is mostly self explanatory.
Note the arrangements of the GNDs (all connecting up) and V+s (all connecting down).
Most modern electronics doesn’t have a “story” to tell. Most of the PCB wiring will vanish into a microcontroller with several hundred pins or an FPGA with several thousand. All the processing of signals happens in the internal code or gateware and isn’t visible at the PCB level. It’s like a movie where all the dialog happens within the minds of the actors and all you see are external actions that they perform for undisclosed reasons. Probably a coarse block diagram gives as much guidance as a schematic you’ve spent hours fiddling with.
We’ll see how long your contraption will continue to live in firmware when I snip the power supply lines. 
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The story is about the connected peripherals.
The microcontroller or FPGA is pretty useless as a stand alone IC. It needs connections going places. 
Sure it does, but the nature of such digital circuits is very different from analog circuits. Take for example the headphone amplifier I showed above. The schematic is set up a bot “roomy”, and wires between parts are short and everthing is logical, and there are very few labels (A few for power, and Left / Ritght for the outputs, and that is about it.
With digital circuits there is a lot of stuff connected to a uC (or FPGA), but where it gets connected to that IC is often pretty much arbitrary. It really does not matter much whether you draw such things with wires or with labels. They are just connected to I/O pins (or SPI, I2C, Timers, etc). For a bunch of my “simpler” uC circuits (Built on matrix board, so no PCB either), I have not even bothered to draw a schematic at all. Things like relay drivers or an SMPS module are pretty much self explanatory. For the rest the “schematic” is only in one of the header files for the firmware. It has a list of all I/O pins used, their locations and function and name of what it’s used for. Maybe a few sensor IC’s hanging on an I2C bus. It would be trivial to draw a schematic for such a project, but it also would not add much, and there is the risk of firmware and documentation going out of sync.
I agree with everything you mention; BUT, we have a newbee OP and when he hits the ERC, or tries to create a PCB with his posted schematic; there will be some “minor” problems.
IMHO it is best to start with small steps and draw some wires and connectors.
I agree we may have strayed too far from giving the OP concrete advice. Here’s mine:
- The MOSFETs and the motors should be in the same block. They’re directly related one-to-one.
- Arrange the blocks left-to-right as SENSORS => PROCESSING => MOTORS as that’s probably how the signals flow.
- If a net is long and/or meanders from pin-to-pin, then just place net labels on the pins. Nobody wants to trace a long line from one pin to another.
- Even if a net is short and goes only between two pins, place a net label on it that represents its function. This provides more information about design intent whereas a line from pin P2 to pin A7 could mean anything.
- Put your power connections in one place (along with the POWERFLAGs) and place net labels on them. Then attach power/ground by placing the net labels on the pins of your parts.
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