Marth's tech chasing is amazing. D-throw is good at any percent, and will set up a tech chase, where f-throw won't cause a knockdown until ~10%. It's a great way to get a feel for your opponent, since you'll be seeing their tech habits, however as you go up in skill their habits are harder to read.
Your dash dance length and Marth's speed are really good for reaction based tech chasing, if you're opting for more grabs, and is a pretty big part of the Marth/Falcon MU. You'll want to tech chase Falcon to roughly 30% (or get him off stage), mixing in pummels for a bit of extra damage (my rule of thumb is 1 pummel for every grab after 7% and goes until 20%, and then 2 after).
Mixing up tech chases with your up throw is also good under platforms, and is a good way to make your opponent mix a tech, resulting in a potential hard punish.
Against the space animals you can use a d-throw after a few up-throw regrabs; this can catch them off guard, and make them miss the tech where you can f-smash them for free. If they tech, however, Marth is fast enough to react and get a regrab.
Sorry if my explanation is a little long winded, but I figured I could give you a few examples on what you could do off of throws and tech chases.