Yes, cutting down on the booze is always a great thing for guys who want to last longer in bed and/or have better erections, so you're on the right track as far as that goes.
Mind you, at least 30 minutes is a bit ambitious. While premature ejaculation is sometimes defined as "not being able to have sex for as long as you want to", you're generally really not considered to have a problem unless you can't have sex for three minutes, and sometimes, the requirement is even that you climax before intercourse even starts. Half an hour is a bit of a stretch! If you ask your doctor how to last longer in bed and you go longer than three minutes, he'll probably tell you nothing is wrong with you.
I'd advise you to masturbate regularly, and to have sex more often, if you want to last longer. This way, it takes longer to ejaculate. You can also pause when you start getting closer and let the arousal come down a bit before continuing.
Sex is an extrarodinary experience, blending emotional, physical, psychologial, even (or especially) spiritual elements and energies, and alcohol simply gets in the way.
There are several questions that you might consider before I suggest answers.
There are no correct answers to these questions, but they may inform (improve) your own decisions as you think about them.
Why do you want to last long in bed?
- to impress your partner?
Does he/she demand that you last longer? Have they expressed concern? Do you hope to be thanked afterwards?
- to enjoy the sex more?
If you join the army, you will get very fit and last longer, but no one suggests that army soldiers are sensitive.
What does 'lasting long' look like?
- pushing in and out for thirty minutes?
Unless he or she owns an oil factory, they are likely going to resent being monotonously pistoned in/out for that length of time.
- enjoying a sexual experience with your partner that leaves him/her continually aroused, excited, and satisfied?
Then it's not 'lasting long' that you need, but paying attention, and delaying the point where you 'get serious'
As to the answers, briefly, these are some of the commonly accepted responses:
Bear in mind the above, that sex is physical, emotional, psychological, spiritual
Spiritual: You are designed to orgasm, and designed to enjoy it:
- deadening your own experience to impress your partner may not impress your soul, and leave you bored and disconnected
- appreciate the joy, sensuality, look, feel of your partner as you would a meal, and only 'piston' in and out at the end of the meal
- connect with your partner and appreciate their feelings/experience - distracting you from your urge
- slow down, be still (you can give great pleasure to a woman by being still)
- stay deep (inside) with gentle pressure, to maximise her pleasure, while maintaining yours on 'slow boil'
- vary the session - some intercourse, some cunnilingus, some massage, finish with intercourse for dessert
- tugging the balls, though I suspect this is most effective when done by the partner, apparently 'drops' the level of arousal
If in doubt, you can use the trick that fear is more powerful than pleasure, every time:
- think of something 'fearful'
- a friend walking in and catching you, parents walking in, police walking in, whatever
- think of something else
- compose a thank you letter to her mother for the dinner she cooked
- if you can still keep an erection after that, you're a miracle worker
[French joke: the real man is not the man who walks in on his wife having an affair, and says carry on, to the man; it is whether or not the man can carry on]