1. If you're new, realize that your muscles will get stronger faster than your connective tissue. Be patient with your progression and be mindful of joint problems.
2. Most of the powerlifting/strength training programs are a bit light on pulling. Add in pullups and rows if the program doesn't call for it and your posture will thank you.
3. Strength training isn't cardio. It should (eventually) be hard. If you're taking one minute set breaks on big lifts you're doing it wrong.
4. Learn to eat. High protein and adequate calories. If you don't eat well you'll struggle to progress after a while and you're likely to get injured becasue your body can't recover adequately.
The author, or another prominent advocate on YouTube, emphasizes the ability to get a workout done in under an hour. In my opinion this is rushing it.
There's a joke that you should add 5 minutes to your warm-up for every year over 30 (exact numbers vary). The point remains: always warm up thoroughly, especially the older you are.
I take a lot of time between sets to recharge my ATP. I also do days where I'm not trying to add the 2.5 kg, but instead focus power. Or even just do it with good form at a slightly lighter weight if I'm not feeling 100%. The newer you are to lifting, go slow and focus on technique. (Perhaps 20 year olds can add 2.5 kg every session ad infinitum but I can't.)
A coach is a great resource, but a) most trainers in gyms are not strength coaches, and range from actively harmful to wonderful, and there's not really any way for the novice to know which they are, and b) legit strength coaches are expensive. I'd recommend self-study and starting lightly before a coach, personally, but if having a coach is the difference between you lifting and not lifting, get the coach.
Alan Thrall has 3 really good beginner videos on the S/B/D movements:
* https://www.youtube.com/watch?v=bs_Ej32IYgo
* https://www.youtube.com/watch?v=wYREQkVtvEc
* https://www.youtube.com/watch?v=BYKScL2sgCs
Also check out the JTS pillars series. JTS are legends in powerlifting, and these videos can really help tune up technique.
* https://www.jtsstrength.com/pillars-squat-technique/?v=7516f...
* https://www.jtsstrength.com/pillars-bench-technique/?v=7516f...
* https://www.jtsstrength.com/pillars-deadlift-technique/?v=75...
There's also https://www.reddit.com/r/formcheck (and r/fitness and r/stronglifts5x5) which can be valuable resources for getting help fixing particular problems.
It's kind of funny. I've seen people afraid to try lifting a 20kg barbell in a controlled, slow movement, even though they don't have any fear at all about picking up their nephew or lifting a bag of dogfood.
I work out in a "group personal training" setup where there are generally 5-8 folks lifting at a time, usually performing the same lifts on the same days, but all at different paces and levels. And we have a coach that helps with programming and offers assistance, critique, and timely doses of motivation or ridicule.
The most important thing is working on form, which you don’t have to do with heavy weights. But for this a coach totally helps because they can pin point exactly where you’re messing up.
https://smile.amazon.com/Starting-Strength-Basic-Barbell-Tra...
If you wanted to get really picky, it lacks lacks arm (bicep and rear deltoid, primarily) and oblique accessory work, but I don't really consider those too big of a problem since most beginners need something straightforward that isn't too overwhelming.
In terms of programming, it has some deficiencies, but most people just need a structured program to start with. You can probably run it for 12-18 weeks and then have a strong foundation to switch to another program. People argue its deficiencies, but if it gets you started and gets you structure to build a routine with, that's what you need, IMO.
For the last couple of years, I've been training with Jim Wendler's 5/3/1 program, and it's fantastic. I keep getting stronger and can probably happily train on it for many years to come. I've competed in a couple of local powerlifting meets, and have a routine that I feel like I can sustain forever. There is a 531 for Beginners program, too, but it's less hand-holdy than Stronglifts.