I’m afraid that’s a hard one and takes a great deal of time and patience to get a feel of pacing, and I’m always learning it myself! Timing is a critical skill and one that you can only learn by practice, practice and more practice, but you can also observe it in good comics and other media.
As an exercise, find a comic that you really enjoy and ‘moves well’, and have a look at when and how they use different shots like close ups and establishing shots. You’ll see the same devices in films too, so watch a film you enjoy and see if you can pick out the similarities; this category of study is often called ‘cinematography’ but when it comes to the timing in comics it slides into another realm all of its own. Draw thumbnails (tiny pictures) of each shot in a scene that you like- look at how are they moving the camera, where the characters are in the frame, how they have used shadows and lighting etc.
On top of this think about the juxtaposition of one shot to another; What is the effect of having a close up immediately followed by a wide
shot of the same character? They feel very small. What is the effect of
having one character viewed from a worm’s eye view and then the other viewed from a downshot? The first character feels imposing, the other feels powerless. Context is everything in comics because these devices can also affect the flow of time- big, open shots feel like they hold a lot of time, while a succession of small frames with similar content flow one after the other like seconds in a film strip. Slashed, diagonal shots feel more dynamic and quick, and long horizontal shots are slower or can even ‘freeze’ time, like a held breath. Contrast is very important- a long horizontal panel feels much more poignant after a page full of narrow panels, and a full page spread usually only follows a lot of pages with many panels. Use special panels sparingly and they will add a huge kick to your comic, but drown people with them and the comic flow becomes too hectic.
One big tip is to watch out for a type of shot or panel that you seem to use a lot; lots and lots of the same thing can be very dull, and some comic artists fall into the ‘head and shoulders’ trap where you almost only ever see that part of the characters with next to no background. Unless you are doing it on purpose for artistic effect try not to get too samey with your shots. That’s about all I can suggest, the rest is down to hard work and practice! Good luck!