Before you can answer this, you must know what the term "dramatic techniques" encompasses. Dramatic techniques are tools the playwright uses to create theatrical, dramatic effects in a theater performance that can be uniquely applied to theater or to a play cinematographically rendered as a movie. Some of these dramatic techniques are:

• soliloquy
• aside
• speech directions [except for [Reads] [Song] [Sings], speech directions are not given in Twelfth Night because emotive affect is manifest in Shakespeare's language]
• stage directions [e.g., "Enter VALENTINE and VIOLA in man's attire"]
• off-stage [i.e., action or speech occurring off-stage]
• music
• song
• dance
• entrances and exists [e.g., entrance of a key group or at a key moment: I.iii Enter SIR TOBY BELCH and MARIA]
• speech length [affects tension, suspense, pace]
• set and set changes e.g., Orsino's palace, sea-coast, Olivia's house]
• lighting in stage/set directions [e.g., creating emotional and psychological effect]
• costuming [e.g., important to premise, as with Viola in Men's clothes, and to theme]
• rhetorical language [e.g., setting the tone of the play]

In the first two acts of Twelfth Night, there are a few prominent dramatic techniques. Rhetorical language is soon evident in Act I.i in Viola's use of apostrophe (using "O" to address someone who is dead or not present): "O my poor brother!" Act II.iii introduces music and song when the Clown leads in a song: 

Clown
    [Sings]
    O mistress mine, where are you roaming?
    O, stay and hear; your true love's coming,
    That can sing both high and low:

In Act I.iv, Viola uses an aside to enlighten the audience on her thoughts of her infatuation with Orsino. An aside is a short speech spoken in the company of other characters but delivered directly to the audience that represents the character's private thoughts and is thus unheard by any other character.

VIOLA
    I'll do my best
    To woo your lady:
    Aside
    yet, a barful strife!
    Whoe'er I woo, myself would be his wife.

Olivia later uses a soliloquy in Act I.v to muse over her reaction to her conversation with Viola/Cesario. During her short soliloquy, she expresses a readiness to be infatuated with the new Cesario, A soliloquy is a private speech spoken by a character in solitude that presents the character's inn er musings and psychological expressions:

OLIVIA
    ...   
    Even so quickly may one catch the plague?
    Methinks I feel this youth's perfections
    With an invisible and subtle stealth
    To creep in at mine eyes. Well, let it be.