Summarize the following:
You put in lot of hard work, you you have the facts and the content, but if you do not know the proper way to convey the message then you can lose out to others. Or somebody else who is a good talker might take the credit for your hard work, which can be extremely frustrating.  Therefore, it's important that you learn how to speak up for yourself and that you do not hesitate to speak wherever and whenever necessary about what you can do, what you have done, your strengths, capabilities. You may prefer to work behind the scenes silently, but it is equally important for you to take center stage from time to time if you wish to make your mark. If you are unwilling to be assertive, remember that there are scores of other people out there who are prepared to walk all over you in order to move up the ladder. You can prepare and practice what you would like to speak, but also remember to practice how you would like to say what you intend to say. Practice the right pace, intonation and pitch to deliver the message.  Being an introvert, you would probably find interrupting somebody rude and would prefer not to do it yourself. But, keep in mind that extroverts or the good talkers are usually good at interrupting/interjecting the speakers, when somebody interrupts your mind goes blank, you feel like escaping from that place with all the eyes fixed on you and you not knowing how to and what to respond. Such incidents send jitters or scare you or make you retreat into oblivion. So, practice how you would face them, what you would say in such case, how you would respond, how you would tackle it …because introverts are usually not extemporaneous speakers and need time to prepare. So it really helps to be prepared to speak up. For example, when somebody interrupts you you can politely but firmly ask them to wait till you finish, or that you have allotted time for questions at the end of your presentation and so their question has to wait. Since introverts are better at writing than talking, you can use this characteristic to sell yourself, showcase your work and project and yourself as a capable worker.  Since you feel more comfortable communicating in writing than talking, produce effective e-mails to strike the right chord and to convey your  message in the most effective manner. You can develop the skill to communicate in writing as if talking to them. Since you have excellent attention to detail, are focused and strive for perfection, you can also be an extremely good choice for writing important documents such as proposals and business plans. You can also showcase your work using professional networks such as LinkedIn as well as social websites such as Facebook and Twitter. Introverts often find it somewhat discomforting and disconcerting to be vocal in meetings, brainstorming sessions and discussions. This can put them and their careers at risk. To mitigate the risk, introverts should use their writing skills.  For example, after the meeting, brainstorming session or whatever it is you could send out an e-mail stating your observations on the particular topic, your views and suggestions, or any other data to substantiate your position. What's effective about this is that everything you say can be substantiated by evidence, research and deliberations, which creates a good impression Additionally, putting your thoughts in writing saves you from having to do the talking. So, the question of getting confused, going blank, or experiencing discomfort due to the presence of a lot of people can be avoided. Also, if you need to commend a subordinate for his or her good work and are at loss for words, you could use the power of writing. However, keep in mind that the technique works best when writing is used in combination with a certain amount of face-to-face communication. Prepare not just in terms of what the content would be, but also on how you plan on delivering the content in terms of the pace, pitch and tone.  Think about the possible questions you could be posed and how you would respond to those questions, how you would respond when somebody interrupts your speech/presentation, how you plan to break the ice in the room, the best strategies to attract the attention of the participants and what strategies to adopt to lighten the atmosphere in the room. Dealing with too many people at the same time and too much conversation can be exhausting for an introvert, particularly if you are unprepared. Therefore, it's important to practice in order to strengthen any weak areas.  By repeatedly doing this you will get used to handling meetings, presentations, questions with confidence and assertiveness over time. You do not have to try to change your personality entirely or become an extrovert, but sometimes you need to tweak your personality a little to suit the occasion. Make it a point to attend events - it is important for you to be seen in social and office circuits.  However, try to arrange social events so that they don't make you feel too uncomfortable. Just because you go to an event doesn't mean you have to be there from beginning to end. Arrive on time, say your hellos, talk to some ‘must meet’ important people and leave. Or, instead of scheduling meetings over lunch or dinner which can take longer and be more stressful, you could arrange to meet over coffee. Before you attend a social event, prepare some conversation starters in your mind. Prepare specific topics depending on who you will be talking to - you boss, you employee, a man, a woman, a client, etc.

Summary:
Try to be more assertive. Practice speaking in front of others. Make the best of your ability to write well. Make your opinion known, one way or the other. Prepare for any meetings, presentations or discussions in all possible ways. Push yourself to be more sociable.