When you are performing on stage, on your own, rehearsing over and over can sometimes lead to a monotone. Unlike performance dialogue, you have no one on stage with you to bounce off. That can leave you at the mercy of your own idiosyncrasies.
The following guidelines and tricks are some of what I use to escape my idiosyncrasies, hope they are useful to you too.

Performance should reflect your intentions.
(Let’s call it performer’s intent). First we will cover some vital questions to help you shape your intent.

Who are you?
Who you are may be a protagonist. But, it’s important to define who that is if that’s the case. Define your character with a purpose, or defining attribute not name and or age.

Who are you talking to?
Identify and specify an intended audience. What language do they speak. Where and how do the live? You will address a five year old different than you would address a 45 year old policeman, so your intonations should reflect who you are talking to. Once you define who you are talking to, you can look for commonalities and differences between you and your intended audience.

What are you trying to say?
What is your intended message? How do you want people to feel? (devastated, elated? etc) The purpose of the content, should come through in the delivery.

All of the above questions would ideally have different answers from each person. That individuality is what a performer can draw from, to create an authentic, unique performance.

With the above ideas in mind, the following little tricks can help expand your versatility. You can apply the above questions to an entire performance set, and also to each line.

Like any tool, they only work if you work them. Choose tools as you need them based on the answers to the initial question.

Hat Tricks

For the below hat tricks, you can use the sentences in italics to experiment with the tool that’s being discussed.

Pace Control
Exercise your speed. Recognizing when to go fast, when to pause, and when to go slow can be powerful.
Saying something very slowly can be powerful.
Use it wisely.

Maintaining the fluid ability to change pace at will, is only achievable when you can also go as fast as you want too.
Say things in fast forward. As fast as you can, while only missing syllables that are permissibly missed in the dialect or accent you intend to speak in.

Emotional expression
-Intonation;
Pitch variations
I can deep down my voice, but my exercise for high pitch is an excerpt from Under the sea, From The Little Mermaid.

Under the sea,
Under the sea,
Baby its better, down where it’s wetter,
Take it from me.

I prefer to attempt it in the shower, at times that there’s no unfortunate casualties in hearing shot. Bear in mind that the more you can brave embarrassing yourself, in front of yourself, the less scary it is to stand in front of people, so push yourself out of your comfort zones during rehearsals.

-Body language
Look at your full body in the mirror and attempt different postures. Put yourself kneeling down, begging, or stand as a king would over imaginary subjects. Body language can be spit into a few smaller bits that combine to form your overall body language. Posture, Arm movements and Footwork

-Posture
Look at the physical postures people around you have, extend your posture out of your comfort zone while rehearsing. Get comfortable in postures that are not natural to you, and increase your on stage flexibility.

-Arm Movements
Be conscious, when the stage is yours, that it is yours. When you rehearse, compare wide extended, owning hands to arms folded across your chest. How high up on your body do your arms go, are you intimidating, or embracing your audience?
Are you cowering away from them?

-Footwork

Where are you going? Where does it look like you are going? This can be anything from military still, to Dancing in between. Even moderate movement can signify a place and or time has been crossed.

-Facial variations

Even when addressing downcast content, the variation in one piece can accentuate a particular emotion. When you are describing sadness, it often involves the loss of something. Describing the thing that is lost, helps your audience understand and feel the loss themselves. In this case , meet variation in content with variation of facial expression. I suggest sitting in front of a mirror, and looking back on past experiences,(eyes closed at first if you’re shy, then when you feel something, you weren’t feeling before, open them). Take a look at your palette of expressions and don’t be afraid to use them when you think they could be appropriate. I would advise against forcing smiles, unless you are meant to be doing a forced smile. Your audience can feel your emotions, so the best way to vary your facial expressions, is to call apon the feelings that inspire those expressions, not to change your face alone.

-Vocal variations
Consider volume, but for the most part reference the different ways that people have made you feel when they have spoken to you. Try out those ways. When you rehearse, reference the people around you. Mimic if you can. Mimicking can be complement as well as insult. When you are just starting out, shout during some of your rehearsals, get comfortable with hearing your voice loud, that way you wont communicate embarrassment when you are trying to impersonate a dictator.

Clarity and Audibility
Try out differing spaces when you rehearse, bigger rooms spread sound out more, differently shaped rooms spread things around differently. You may need to face more than one direction to project to a whole room, in the case of sound equipment, do a sound check, whenever it’s possible. Mic control does well with practice, so grab any appropriate times to test out different mics, and different ways of holding your microphone. Beware of Ps, Bs and Ts, try to angle your microphones in such away as not to push air directly into it when you say them, or they will cause feedback.

-Enunciation
Pronounce words in the way that you want them pronounced, if you practice different pronunciations, you increase your versatility. Who your audience is, and who your character is will have great bearing on what kind of pronunciations you use.

Overall, try to sound, look and feel how you would like to be understood, use variations in pronunciation and accentuation that take you closest mentally to the places you are trying to take your audience.

Which brings us to the last bit:

Audience Interactions

All of your audience interactions will give you an idea of your performances effect on them. Compare that to your initial intentions of what you want to say. Remember this: No one audience can define your worth as an artist. People differ, so if you don’t get the reaction you wanted, you can try changing a thing or two, but don’t take it to heart to the extent that it stops you from performing. The entire process is trail and error, use their reactions as a feedback tool, not for your own gratification.

-Eye contact
Look at people when you can, before, after, during a performance, they will express different reactions to you, and that is your truest feedback.

-Listening
Try to understand different types of audible audience feedback, volumes and timings of applause, the difference between a tension laugh and a mirthful one. How are they sitting? Are they moving around in their chairs, or are the dead still. Keep your ears open to their feedback.

-Prompting Feedback
Call outs, chants, and questions can be a way to hear back from your audience to guage their mood. Every way that you can receive feedback will tell you how your initial intention was received.

NB. I’ve seen a performer do this before, so please don’t make this mistake: DO NOT ask or demand for a standing ovation. Speaking as an audience member, it is extremely off putting. Standing ovations are a spontaneous voluntary compliment and should never be demanded.

Keep your process flexible

Sometimes a different and better outcome can come out at the end of the process, but putting the time into it can help you refine, what to change your mind about. Bear the first questions in mind when you record your rehearsals for review, and when you have the opportunity to have someone to practice for, ask them how your presentation made them feel.