If you are into travelling light but don't want to a freak about it (by weighing everything), get a luggage scale to weigh your backpack after you cram everything into it. Then start taking stuff out before you start buying the lightest things you can.
Top weight saving things:
1. UV water purifyer
2. Pak Lite
3. Decent running shoes or the like
if your just going to walk on trails. Sturdy footwear for more rugged/colder hiking. Bet you could do summer PCT in California in just good shoes.
As always, your mileage may vary and yeah, do a few all day hikes to see if you want to give up you trusty Limmers.
4. Olive oil for calories vs bulky food. Still need fiber though. Learn to 'skip' meals...woo, intermittent fasting
5. Leave the drugs at home
6. You don't need a guide book, figure it out beforehand....that is what your brain is for.
7. A friend swears by the versatility of the jungle hammock (tent and bedding in one!)
8. Embrace your inner dirty self and get over the filth factor ASAP. You do't need a clean pair of daks for every day you are on the go.
9. Leave the 454 Casull at home.
There are many tips in the world about lightweight hiking and you can go down any sort of nerd hole, er, rabbit hole of trying them all.
Just keep things simple and wait till you are climbing K2 before you go off the deep end.