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
If you have a perpendicular shape, like a plus sign, usually what I was taught, right whole side of the "plus" sign are negative. The left side is positive. I think it's how you say it.