Ruby -p, (削除) 141 (削除ここまで) (削除) 140 (削除ここまで)(削除) 137 (削除ここまで) 137131 bytes
Saved 3 bytes by using $$%10 instead of rand(10), a golf suggested by @NahuelFouilleul in comments on other answers.
$_="How to#to #{v=$_[8v=$_[9..-2]} in #{n=1+rand(10)n=1+$$%10} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+vnot '+v:v[/\w/]v.upcase+$'capitalize}."}*''
Ruby -p, (削除) 141 (削除ここまで) (削除) 140 (削除ここまで) 137 bytes
$_="How to#{v=$_[8..-2]} in #{n=1+rand(10)} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[/\w/].upcase+$'}."}*''
Ruby -p, (削除) 141 (削除ここまで) (削除) 140 (削除ここまで)(削除) 137 (削除ここまで) 131 bytes
Saved 3 bytes by using $$%10 instead of rand(10), a golf suggested by @NahuelFouilleul in comments on other answers.
$_="How to #{v=$_[9..-2]} in #{n=1+$$%10} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not '+v:v.capitalize}."}*''
Ruby -p, (削除) 141 (削除ここまで)(削除) 140 (削除ここまで) 140137 bytes
$_="How to#{v=$_[8..-2]} in #{n=1+rand(10)} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[1].upcase+v[2.v[/\w/].-1]upcase+$'}."}*''
Ruby -p, (削除) 141 (削除ここまで) 140 bytes
$_="How to#{v=$_[8..-2]} in #{n=1+rand(10)} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[1].upcase+v[2..-1]}."}*''
Ruby -p, (削除) 141 (削除ここまで)(削除) 140 (削除ここまで) 137 bytes
$_="How to#{v=$_[8..-2]} in #{n=1+rand(10)} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[/\w/].upcase+$'}."}*''
Ruby -p, 141(削除) 141 (削除ここまで) 140 bytes
$_="How to#{v=$_[8..-2]} in #{n=1.+rand n=1+rand(10)} easy step#ste#{n>1??s:pps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[1].upcase+v[2..-1]}."}*''
Ruby -p, 141 bytes
$_="How to#{v=$_[8..-2]} in #{n=1.+rand 10} easy step#{n>1??s:p}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[1].upcase+v[2..-1]}."}*''
Ruby -p, (削除) 141 (削除ここまで) 140 bytes
$_="How to#{v=$_[8..-2]} in #{n=1+rand(10)} easy ste#{:ps[0,n]}!
"+(1..n).map{|i|"
Step #{i} - #{i<n ?'Do not'+v:v[1].upcase+v[2..-1]}."}*''