Conference calls are be the frustrating and least fault-tolerant part of my day. 

Here's a few tips that help me smooth the always rocky experience of conference calls:

1. When you get on the call, announce yourself.
   This cuts questions short about who arrived and who's missing and the seemingly inevitable carrying on.  Depending on how formal you need to be, "Dylan here" and "Dylan Thomas, joining the call" both work. Worry less about interrupting than sneaking in, because they're probably waiting for you anyway. If you're late, just blame it on not being able to get in, no one will challenge that.
2. Show up early (with your team). It saves time and makes you look good.
   I've been known to call in 15 minutes before an important conference call. If you show up 5 minutes early, you have time to deal with all the kinks that come with conference calls, and potentially can alert others so you don't waste half an hour wrangling everyone because the wrong code was sent out. Also, this allows for some quick strategizing and informal talk with your colleagues.  When your clients show up, they'll be pleasantly surprised that you're ready to roll and the positive momentum is on its way.
3. Keep your on-demand conference call-in info in an email template, and in a note on your phone
   No more digging through email, logging into sites, copy and pasting just because you need to resend the info to someone (or have forgotten it yourself). Gmail canned-messages serve the same purpose and have saved my bacon more than once.

While these practices seem obvious, most people don't use them. I hope this helps make your day a bit better and your calls more productive.

A note on providers:

If anyone could suggest a bulletproof conference call provider, please let me know. I've tried many, and finding one that doesn't randomly drop participants, lock people out, or get static-y right when you get to the important part is more difficult than it should be. It doesn't seem to matter whether they are free or cost thousands of dollars a month or whether it's landline or VOIP based.

I tend to cycle through conference call providers as their quality ebbs and flows. Don't be afraid to switch if your provider is no longer up to par.

My current favorite is Freeconferencecallhd.com. So far I've been impressed. It has the best call quality I've ever experience and I've yet to experience any weird call dropping, locking out, or other connection issues. It's also optimized for VOIP and lets you call in via Skype, which is a nice bonus, especially for international calls.