When you are first starting with Arduino, you may find that things don’t work exactly as you expected. Here are some tips to help smooth the way for you.
COM ports
Make sure that the IDE is set to the correct COM port. (Find this under the Tools menu.) This option is not available until the Arduino is actually connected to the computer through a USB cable.
Buttons
Toggle buttons can often be frustrating for beginners because they work inconsistently. This is because buttons need to be debounced. Learn about that here: How to De-bounce Switches on the Arduino – Circuit Basics
LEDs
Make sure that you add a resistor in series with an LED, otherwise you can draw too much current and burn out the LED.
Pull-up and Pull-down Resistors
In order to get digital inputs to work properly, it is really important to understand the need for pull-up and push-down resistors and how they work.
Arduino Pull-up Pull-down Resistor | Arduino FAQs (arduinogetstarted.com)
The Arduino is able to use internal pull-up resistors: Digital Input Pull-Up Resistor | Arduino Documentation
Motors
You can run a motor by connecting directly to the Arduino, however, depending on how much current the motor draws, the motor may not run well or may damage your Arduino. The proper way to control a motor is with a transitor or a motor driver. See this tutorial: Overview | Arduino Lesson 13. DC Motors | Adafruit Learning System
Power
The Arduino can be powered by keeping it connected to the computer, connecting directly to an adaptor, or connecting it to battery. Some circuits will require more power than a battery pack can supply. In addition, an Arduino can run down batteries within a few hours.
CoMo Science 
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