Decide how you want to play Adam early on
Playing Deus Ex boils down to one of two ‘modes’ – Lethal or Non-lethal.
The path you want to play will determine almost everything about how you play: what weapons you need, what augments you upgrade, and how you spend your cash. This is all vital.
Deus Ex is ultimately an RPG, and it’s about choice. It’s recommended you make a strong decision on how you want to play from the very moment you press New Game. If you waste cash or Praxis Points on skills that you later won’t use, you’ll have wasted those resources.
Which sounds better to you? Running and gunning, or stealth-based antics, crawling through air vents and taking out enemies silently? Both will broadly speaking reward similar amounts of EXP, so pick that which sounds more fun to you – then spend the game buying skills and building towards that. Because Deus Ex is a more compact and finite RPG experience, you won’t have the opportunity to grind for experience forever to unlock absolutely everything.
Don’t waste experience on things you won’t use regularly, and remember that every single part of the game can be played either way – even when you encounter bosses, you can take them down non-lethally.
There’s also an achievement for playing the entire game without a kill, if you’re so inclined.