As soon as you know you are to make a speech begin making notes

Research your audience/education level/demographics/ specialisms

Search for a novel approach/angle to your subject

Discover something dramatic to grab attention

Consider posing a question, if you can make it relevant & interesting

Consider using a relevant introductory story. If so keep it short

Assemble ideas in a logical order

Plan to be as general as possible, use detail only when it is necessary

Consider timing

Plan for the shortest speech that does the job, within reason

Allow enough time for lots of rehearsals

Plan an opening quotation or theme that will grab attention

Be aware that you speech will be remembered good or bad

Be aware that your speech may be videoed, especially at a wedding

Plan your dress to suit the occasion/audience

Consider what you will write the speech/cue cards on. Index cards are good

Notes/cue cards

If you write your speech try to plan to not appear to be reading it

Consult a thesaurus

Print out your speech in huge type so you can read it very easily

Highlight words/passages that need emphasis

Plan referrals during the speech to the main theme

Write as you plan to speak/use colloquialisms but not slang

Build in references to the venue/occasion/audience

If jargon is appropriate to your audience plan to use it

Check your speech has a clear theme/aim

Check that it achieves the purpose you require

Check that it is internally consistent/hangs together

Check that it is as simple/accessible   as the subject allows

Prioritise points in this order 4-1-2-3, 4 = most important

Check for repetitions/padding and eliminate

Plan a neat ending that sums up and rounds off without being obvious

Rewrite the speech as many times as you need to

Consider recording or videoing speech