Lift the pot and feel the dirt in the top of the pot to know the water content. Don’t overwater, don’t underwater. Learn how much the plant needs.
When I say ‘feel the dirt’ i mean stick your finger in.
The reason I say this is because the MOST common mistake by newbies is overwatering or underwatering.
KISS. don’t forget to KISS
Learn from your mistakes. Have patience. 
SIP’s are the best thing since sliced bread and are the easiest style for new growers! Takes over/ under watering out of the equation.
KNF, JADAM… JMS and IMO FPJ and FFJ to be specific.
Also start a bin. No, really , start a fucking worm bin! Now!!
If you make a change, only change one thing and give the plant time to react to see the effects of your one change so that you can better understand what change had what effect
Take notes on everything, and take measurements! (Get a cheap light meter, a cheap humidity sensor, etc)
and always always always keep learning and researching
My suggestion would be take things slow and don’t do to many things at once it’s easy to think of throwing everything and the kitchen sink at your plants but then you won’t be able to properly learn from it the turtle wins the race or however that saying goes
Be simple, be clean, be patient, be organized, be motivated, be knowledgable, be curious, be careful. Be thankful.
Be highly Medicated!
Make a lot of growmie friends that you can ask for advice when you’re struggling. If you have reliable friends, it’s a huge knowledge pool that comes in clutch when you don’t know what to do or need assistance.
Keep at it.
Keep growing. You’ll get better every time.
Uh oh… only a few likes left today… I better make’m count 
oh man, y’all making it soooo hard for me
Join OVERGROW!!!
Buy the cannabis growing bible and never read it.
re-consider LITFA as this hobby will consume your life, your money and your soul
My best piece of advice is have fun and don’t stress!
i like this advice very much. it’s not something that a grower, especially new, would think about. but it makes a lot of sense in order to isolate issues and troubleshoot. @herojuana.tom you get first pick
Integrated pest management. 
My best advice is don’t overreact and throw solutions at the first symptom of what you think is a deficiency, and buy a real ph meter.