Declamation offers the distinct challenge of merging your interpretation and speaking style with another's.  Surrounded by speaking events where you are the writer, no other places competitors into such a predicament.  With the risk of being compared to another orator, Declamation speakers must seize a speech they did not write and caress the words to become theirs.  This feat must be accomplished while still using good speaking skills.  What sounds intimidating can be done by following a few painless suggestions:

1. Look to punctuation.A skilled writer will infuse rhythm, pacing, and pauses into a speech they draft.  Semicolons, colons, hyphens, ellipses, italics, bold face, quotations, fragments, ALL are the tools used to add voice to ink.  If you see any markings or sentence structure that looks special it could be because the author was trying to highlight that segment of text.  Knowing that, as you design your Declamation's delivery keep an eye for these highlights and let them guide you on possible speaking tactics.  For example, if I saw a word in italics I might consider using my voice to emphasize that word (if my interpretation supported the idea that it is a word to stress).
2. Look at the speech's structure.Punctuation is what guides you with every sentence.  Structure oversees the whole speech.  When thinking about creating vocal dynamics considering the piece's overall build may give inspiration.  Locate the climax.  Do the words leading toward it allow for a crescendo?  Also, paragraphs are indicators of a natural break.  Take that clue to breath and perhaps move if appropriate.
3. Avoid Imitation.After you have interpreted your speech it might be a good idea to watch another speaker's performance of it to gather more ideas.  Apply caution though to not steal that speaker's vocal identity.  Always be yourself and never impersonate another; especially if you are using a speech from a well-known person.  For instance, choosing a piece by Christopher Walken does not give you the right to pretend to be him--nor will imitating him place you anywhere near his unique speaking skills.
4. Projection and diction.As always, with every good speaker or performer comes excellent projection and diction.  Declamation is slightly unnerving because you do not have a character to hide behind.  These words are not your own which slows down the process of ownership and delivering from your heart.  But by being heard and understood you add authority to your voice that none will be deaf to.  Here is a great article on how to improve articulation and projection:
5. Variation.Declamation might not be an acting event but variation is essential to vocals.  Listening to a monotone speech is boring and makes mockery of the author's words; they were not written to be delivered flat.  Variation coupled with keeping your energy high will help deliver an interesting, fun piece to watch.  Strategize how to make use of dynamic (loud/soft) builds, tempo, rhythm, tone, and silence.  Look to the script and question what its nature instructs of you.

Declamation speeches are unique in that how you plan your vocals are influenced by the words of another--they are not ones you manufactured.  Because you have a script to look towards, take advantage of this perk and look towards the script for vocal guidance.  A majority of the script may be straightforward, but look closely and subtle clues of vocalization will exist for you to pounce upon.