Step one?
1 ) Open your sinuses & let the sounds ring through your entire head. It sounds way different that way, btw, & gives you more volume, but it's harder for some ppl to retain pitch control this way, at 1st.
2 ) Breathe from your diaphram, not your chest muscles.
3 ) Don't squeeze the notes out through your throat, if you can't hit that note today, don't strain.
4 ) Check yourself often by recording & listening to your development, if you don't have anyone to work with. Check esp for pitch, breath control (phrasing), tremolo shouldn't be done in the throat but through the diaphram, stuff like that there.
5 ) Gradually work on increasing your range. Don't strain.
6 ) Practice daily for 20 minutes straight for the 1st week, working on stretching your range; holding a note without wavering, & then ending with a touch of tremolo; doing those ridiculous "yoy yoy yoy" & "we-you we-you we-you" sounds while you stretch your facial muscles when you go through your scales; inhale through your nose.
7 ) ALWAYS breathe through your diaphram, or your throat tends to tense up, for some ppl.
8 ) After the 1st week, increase your vocal exercize regimen monthly, by 5 minute increments, over the next 6 months.
9 ) Try singing a pentatonic one day, starting at your lowest range. Each time you complete your scale, go up 1/2 step & do it again up & down, until you reach your upper limits. The next day, just sing the 1 - 3 - 5 - 8 - 5 - 3 - 1 of the various keys in your range.
10 ) Try doing a series of 8 note major scales with a "ha ha ha" once in awhile. Remember to push it out from your diaphram. It might surprize you how quickly you tire of that, in a physical way (not just getting bored tired of it!), at least until you relearn how to breathe. 90% ot the world's population don't breathe properly.
11 ) If you have a decent falsetto, try to do a few scales only in that highest register. Note when you need to alter your muscles, the shape of the stuff inside your neck & face, as you go high or low. Learn your limits for each vocal register. Note how the tone naturally changes as you go from register to register, then try skipping one, like going from your lowest to your highest ranges, occasionally. Don't slide into the notes. Hit them dead on.
12 ) Be very aware of your posture. Straight back, shoulders down but NOT slumped (squared, with neck extended upward, shoulders as far from the ears as you can get them, but keep them level, not slumped), standing is always best for singing. Try not to fidgit so much! (LOL)
13 ) When you inhale, hold your hand over your diaphram. Feel how it works as you inhale like you're sucking air through a straw. Go ahead & purse your lips at 1st if you must, to remember this. You'll get the best inhalations, the most air, that way.
14 ) Keep yourself well hydrated. Drink tepid water when you're singing, or a special mix I used to use is pretty helpful, too. Approximately 10 oz water, 2 oz dark apple cider vinegar (or fresh lemon juice, if you must, vinegar's much better overall), honey to taste. Keep it room temp. Some ppl recomend lightly salted water, again, at room temp.
15 ) Experiment with different tones (voices) as you sing. Record them, & choose the ones you like the very best, keeping in mind that there are different tonal needs in different songs & music styles for vocals just as for guitar or bass.
16 ) Practice loudly. You'll find it easier to control things at the softer volumes once you've mastered your range, breath, posture, & pitch, etc, in a loud voice.
Work with a keyboard if you can to continually check your pitch.
That's what I always tell ppl that are starting out, if they can sing at all when they come to me. It's a lot to remember, really. This info is covered in about 8 or 10 lessons, for most ppl.