Well, this is all theory stuff.
if you're switching to a chord say... D
then you need to find the "dominant 7th", which is 5 notes up from the one you're trying to get to in this case D and then you add a 7th so an easy way to get to a D is an A7 chord.
That's why the C7 to F works.
As for minor chords it's a bit different, it depends of you're playing in a minor key rather than the relative major key.
So, let's say you have the chord progression C, Am, F, G, G7
Most simple chord progressions are made up of the Root (C), IV (4) (F), V(5) (G) and/or V7(5,7) (G7) and somtimes vi (minor 6th) (Am)
So we know that this chord porgression is in the key of C
But say you're doing something like Am, Dm, E7
Then this is in the key of Am because in minor keys the IV is usually minor so it becomes a iv which is in this case Dm, and the V stays major but in minor keys is usually V7 so it becomes our E7
If the minor is in a major chord progression then it cannot be altered to a 7 because the next chord is most likely not it's fifth.
But if the minr chord is in a MINOR progression then it can be altered into a 7 because it the next chord ( in the minor chord progression above) is it's fifth.
For different types of transitions, let's say you have a Gm and then a Eb.
Well, if you look at these two chords they have three notes in common, the G, the other G and the Bb
So, you can play these notes while transitioning into the next chord and then play the next one.so if it were tabbed...
1 | 1 | 1
3 | 3 | 3
2 | x | 3
0 | 0 | 0
This is an easy transition.
or you can use a four finger roll. right at the end of the last chord to transition back.
If you have a sus chord then it sounds like it has to be resolved, to be resolved it must return to it's root chord.
so like say you have a G sus(4) then you just return to the G and it sounds good.
If you have this chord progression, Bb, Gm, Eb, F,
then three of the four chords have a common note: Bb
so for a transition, you can have a common picking pattern. like C, D, Bb
So here it is in tab
1 | 3 5 1 | 1 | 3 5 1 | 1 | 3 5 1 | 0 | 3 5 0 |
1 | | 3 | | 3 | | 1 | |
2 | | 2 | | 3 | | 3 | |
3 | | 0 | | 0 | | 2 | |
For the last one though you have to change it a bit so it fits the chord so you just change the last note to an open fret.
Hope this helps a bit...
if not then there are a whole lot of sites on the interwebs that you can find just search chord theory... or something