The current crop of the XMPP-based bots is pretty basic. They provide an online presence in the XMPP network, and you interact with them by a command-line-style interface.
These are some suggestions that bot authors can use to increase your XMPP presence easily. I'm going to stick to easy stuff only, most of it widely deployed.
The first thing that you need to understand is that you can have different per-contact presence information. You can switch the status message and the avatar for each of your contacts. Its called directed presence (basically include the contact JID in the to attribute, but you can always check the spec for directed presence).
You can use this to provide a personalized status message for each person on your roster. If your service has a notion of context, you can use the status bar to show the current context. For example, imagine that you have a ticketing system bot. You type "working on TICKETID", and your bot can change the status message to "Working on: TICKETID - TICKET_TITLE (URL of ticket)".
Optionally you could update the status each five minute with the elapsed time since you started working on it.
You can also switch the avatar. Maybe switch to a red background, meaning that you are busy doing something, or putting it in another way, the bot is telling you that he thinks you are working on something.
Other stuff you should do is to provide an alternative representation of the information you send textually. Twitter (when it used to work...) was a great example of this: every tweet you received by IM, included an Atom entry with the most important information of the tweet. This allows client to improve their interaction with such services, by using a more appealing interface.
But Atom entries are not yet standardized by the XMPP Foundation (there is some effort on Atom over pubsub that could be used as an example though). On the other hand, Data Forms are a standard, and more, they provide interaction possibilities.
You could send a "New ticket" notification, including a data form with the structured information, and a select-box with the possible next steps. The user would see the form, and submit back their decision.
Still in the subject of messages, you should know that there are several types of messages. You have chat, headline and normal (strangely enough the default). There are two more but not important in this context. You should use the correct one depending on the type of message you are sending.
If your system is just sending notification, please use the headline type. It makes it clear to clients that they are not chatting with you, just notifying of something that happened. For example, a smart client can react to those messages differently based on your status: in away, xa (extended away) or dnd, a client can keep a log of new headlines and show it like a email client when you return, without interrupting your workflow, probably using a badge with "You have X pending headlines".
The final recommendation: respect the user status. If the user is dnd, are you sure you should send him anything? Why not change the status message to "You have 5 messages pending. Send 'pending' or go to URL to see them"? Maybe even change the avatar color. You should not disturb someone in dnd. I would also say that away and xa are off limits but that's just me.
On the other hand, you should send "Hey there, welcome back! You have 5 pending messages. Send 'pending' to see them or hop on to 'URL'." when the presence changes to chat or available (not a real <show> value, just lack of <show> value. See the valid values of <show> and their meanings in the spec).
Have fun implementing your bots.
