I'm generally open for suggestions and invitations to speak. I've talked in a dozen countries to both huge and small audiences. Here's some guidelines to make it a smoother process with a higher likeliness of success and happy faces on all sides.
Ask well in advance (preferably more than 2-3 months, probably not more than 9). When I agree to a talk, others who ask for talks in close proximity to that date will get declined. I get a surprisingly large amount of invitations for events just a month into the future or so, and it rarely works for me to get those into my calendar in that time frame.
By looking at my list of coming public talks you can also get an initial clue of what dates that won't work.
Do not assume that I can offer a for-free delivery - I still need food on the table and preparing, creating, traveling and delivering a good presentation takes serious time and efforts. Also, talking at a conference takes away developer time (which is what I actually do for a living).
I will expect that you cover travel and lodging expenses. I don't require fancy, but it needs to be decent.
I consider it good manners if you address the price/charge situation, if not in the first contact email at least in the following discussion. If you cannot pay a speaker's fee, that’s vital information to provide early as it is usually a blocker.
What's the ideal/planned duration of my talk? Between 30 - 60 minutes is normal.
I'm bilingual. I speak fluent English and Swedish. If you say nothing else, I will presume you want the talk in English.
Surprisingly often I get invited to talk without a specified topic or title. The inviter then expects me to provide that. Since you contact me you clearly had some kind of vision of what a talk by me would entail, it would make my life easier if that vision was forwarded to help me produce a talk subject that will work!
Do not assume I know about your conference or the venue. Tell me a little!
I strongly prefer to bring my own laptop with a prepared slide deck. Please don't require me to hand over the slides to you in some fixed pre-determined format (to which my slides need to be converted to and thus causing me extra work). Further, I rarely have my presentation deck "done" until the last minute as I like to keep polishing.
Make sure your projector can do 16:9 screen ratio or tell me in advance.