Improve your passing
There are a number of common problems in passing patterns and a number of tips and exercises to improve.
Slow down. Most patterns become easier to juggle if the pattern is slower and passes are lofty. Go back to 5-club one-count (see learning to pass) to practice lofty single passes and experiment with early doubles (see basic synchronous patterns) to practice double passes. Similarly, beginners often throw heffs and trelfs fairly low and thus fast, rushing the rest of the pattern.
About 110 to 120 beats per minute is a typical reasonable speed for synchronous 6-club patterns, 90 beats per minute is possible to deliberately slow down, and 130–160 beats per minute would be on the fast end. For galloped patterns these higher speeds are common, and for fully synchronized patterns, 100–120 beats per minute is normal (i.e., effectively twice the speed of a normal pattern).
Count out loud to synchronize timing. If running into problems where passers go at different speed, count the passing sequence aloud ("pass-self-self-pass-self-self") to synchronize both passers. Some might find it useful to find music with a strong beat at the right pace – some music apps for runners allow to select music by speed or have playlists for specific speeds (in beats per minute; a 200bpm song works well for 100bpm passing).
Control spin with the arm, not the wrist. A passer can control the motion of a throw at three points: the wrist, the elbow joint, and the shoulder joint. Flicking motions from the wrist can create very fast spinning clubs and throwing with a long outstretched arm from the shoulder joint allows to perform very heigh throws with a single spin – try this solo with a single club to get a feel for the different spins.
To throw slow and lofty passes, entirely avoid spinning the club from the wrist, but mostly throw from the elbow – the same holds for heffs, lofty doubles, crossing double selfs, and trelfs. If the pass arrives underspun, correct it by throwing it higher, not by adding spin from the wrist. If the pass is too short, release it earlier or add a little force from the shoulder joint. It is much easier to get consistent throws with the arm than with the wrist. By not throwing from the wrist, the position where the club is held (e.g., near the knob or near the center) matters much less.
In synchronous patterns, with both passers doing the same thing, it is perfectly fine to throw very lofty passes that are slower than selfs, even if the beats may not be perfectly spaced out in time. The main exceptions are patterns where passers do different throws on different beats (see early doubles and synchronous 7-club pass-pass-self patterns), where it may be necessary to speed up double passes a bit – here, lowering the doubles with a little spin from the wrist might help keep an even rhythm.
Wide selfs, pass to the outside. Passes should be thrown under an incoming self or an incoming pass. There should be no collision problem and no need to throw a pass from far inside (in a scooping motion), or from far outside, or far in front. High and wide selfs are helpful to provide the space. Similarly passes should usually go slightly to the outside, so that the partner can comfortably pass underneath and slightly inside of them. Collisions are typically a symptom of passes that are too short or too low.
Provide feedback. Even if a poor throw is recoverable – for example, caught underspun or caught up-side-down but fixed with a extra half spin on the next throw – provide feedback to the other passer, especially if a problem is reoccurring or consistent. Use consistent terminology, either always describing what is wrong (e.g., "overspun", "too short") or, more constructively, describing how to change (e.g., "a little bit more spin", "longer"). It can be helpful to provide feedback during the pattern, when the problem is occurring, rather than afterward after the pattern fell apart. Especially good passers have a tendency to just correct for problems without saying anything – explicitly and repeatedly ask for feedback.
Watch outgoing passes. Practice to see "through" the pattern and to watch the other passer juggle. In addition to helping with timing, this allows a passer to see how their own passes land and to make corrections without asking for feedback. Start with easier patterns, like 6-club three-count and start watching the other passer more on more, until it is possible to constantly look at their pattern.
Learn to recognize what an underspun and an overspun pass looks like when caught. Underspun passes are often caught (if caught) with the palm of the hand pointing up and overspun passes can be recognized by a quick catching movement with the hand snapping down. Intentionally throw under- and overspun passes to observe this and practice to adjust throws accordingly.
Do not neglect the left hand. Doing only right-hand passes will becoming limiting very quickly, making it harder to progress beyond four-count and two-count. Practice ambidextrous patterns, such as three-count and pass-pass-self or Jim's two-count, from the beginning.
Start at the same time. Even on patterns with doubles, like 7-club two-count and 6-count popcorn, it can be helpful to start at the same time with the common up-down-pass start, even if it means that passer B has to start with a left-handed self. This can make it easier to get the timing consistent, rather than waiting to start "as late as possible".
Let the club slide to the knob. This is somewhat controversial but may be helpful to some: Before a pass, in the downward motion, let the club slide down to the know. That is, still fully grip the handle (i.e., do not swing from the knob), but do this at the far end of the club. This can ensure some consistency in the throws, which is particularly important when spinning clubs from the wrist, but it is less important when spinning a club with the arm.