At the end of someone's transmission, leave a short pause before pressing the PTT; and after pressing the PTT, leave another short pause before speaking. This allows any parts of the repeater system that have delays to catch up (tone squelch, links, Echolink, IRLP, etc).
When calling for Echolink stations in particular, leave at least 4 seconds after the repeater has keyed down before moving on. Echolink doesn't allow the app to “transmit” until the repeater has been completely silent for a moment.
When acknowledging a station, call them by their name or callsign so that they know you're talking to them. Sometimes there are doubles and people might might not be sure who you heard.
Speak slowly, not everyone has great hearing or facilities with your particular manner of speech.
Use the standard phonetics. People get good with their own callsign, but to a stranger, it just sounds like random letters.
If the net lasts for more than half an hour, remember to ID before the half hour mark to follow ISED regulation.1)