1. The vertical asymptote requires the denominator have a zero at that location. The x-intercept requires the numerator have a zero at that location. The horizontal asymptote amounts to a multiplier of the function:
... y = 2(x +5)/(x -3)
2. The vertical asymptote requires the denominator have a zero at that location. The oblique asymptote is an add-on
... y = 1/(x +1) +(x +2)
... y = (x² +3x +3)/(x +1)