The Basic Formula

On the Ground

Combo Fully On Ground

LMH

Launcher, Transition To Air

S

In the Air

Combo In the Air

LMH

Spike, Transition To Ground

S

The Basic Formula with Specials (some steps may not be necessary with certain characters)

On the Ground

Combo Fully On Ground

LMH

Specials

Specials that chain.
Special that puts opponent high up (not as high as a launcher) and you recover fast from allowing you to use L, M, H, or S or jump to go straight straight to aerial combos.
Specials that send opponent away can be followed up by dashing (or teleporting). Sometimes if you catch up fast enough you can catch your opponent in the air with L, M, H, or S or use an OTG special if they are on the ground.

Launcher, Transition To Air

S
(Eggman's Ground Special, "Hedge Killer" acts as a launcher.)

Aerial

Combo In the Air

LMH

Specials

Specials that allows you to use L or M or H again.
Specials that send opponent away can be followed up by air dashing (or teleporting).
Specials that send an opponent down. (Combo may break if S is used before or after special for certain characters and moves.)

Spike, Transition To Ground

S