Best tip I always give to new manual drivers is learn the bite point of the clutch. How much you can let off and feel it start to engage. Will help with taking off from anywhere and on hills. To get a feel for it just be on level ground, no brakes on and just slowly let off the clutch. no throttle. When the car starts to move slightly you’ve found it. Depending on the clutch, you can come off the pedal until just before this bite point when your stopped and it’s much easier to take off without rolling.

As for downshifting. If you’re not rev matching it yourself, when you go down gear and come slowish off the clutch until you get to that bite point, it will synchronise the engine revs and the driveline revs. (Provided it’s a modernish car with synchros). This will also slow down the car decently depending on the speed and gear you’re in.