Hi DevRant ! So me and my friend want to make an app. Just to see how it's done. We're both are okay with C, just learnt Java and we're looking for advices.
Do's and don't, how to get started, good habits to pick up, anything would be appreciated !

TDD (Test driven development) is a really good habit that I recommend

And if you are looking to create an app for android then embark upon android studio :) do not attempt to create apps with gradle on intelliJ, netbeans or eclipse. I speak of experience...

if ( forAndroid ) {
* DO use Butterknife || DataBinding
if ( Butterknife ) {
* DO create XML-Layout first, then
create class with IntelliJ Plugin
}
* DO use Dagger2
* DO use https://material.io/
* DO read/do MVP Tutorials using
Butterknife || DataBinding &&
Dagger2
* DO read up on SQLite and SharedPreferences (saving data)
* DO know Activity lifecycle &&
Context
* DO configue Live Templates for frequently used code snippits
* and for the love of all that is holy
DO COMMENT YOUR CODE AND KEEP YOUR CODE CLEAN1
}

Good Luck!

Three acronyms:
SOLID
KISS
YAGNI