An important part of mastering a language is learning ways to connect your ideas. Spanish has many short phrases which can help you sound more fluent. For example:

En cuanto a - is used like "regarding."

• ¿Qué vamos a hacer en cuanto a esos problemas?
  What are we going to do regarding those problems?

Acerca de / sobre - both of these are familiar terms which are equivalent to "about."

• Quiero investigar acerca de los aztecas.
  I want to investigate about the Aztecs.
• Yo no sé nada sobre este asunto.
  I don't know anything about this matter.

Por cierto / A propósito - these two terms are used like, "by the way."

• Por cierto, necesito un millón de dólares.
  By the way, I need a million dollars.
• A propósito, nuestra tarea es para mañana.
  By the way, our homework is due tomorrow.

Another group of short phrases is used when you need to explain something you've just said at greater length.

Es decir - is commonly used to mean, "that is (to say)," or "in other words," and is used both in familiar and formal language.

• Hemos fracasado. Es decir, ya no tenemos ni un duro.
  We've failed. That is, we don't even have a single cent.

Bueno / Pues - these terms are used like "well" and are often used at the beginning of a sentence while one thinks of what to say.

• Bueno, no sé, la verdad es que no lo he pensado mucho.
  Well, I don't know, the truth is I haven't thought about it much.

O sea - common term in speech (not usually in writing) to mean, "I mean," or "that is."

• No me caes bien. O sea, me molestas bastante.
  I don't like you. I mean, you really bug me.

Vale / sale / anda / venga / de acuerdo - are all used in the same sense as "OK," or "alright." Whereas vale is common in Spain, sale is more prominent in Mexico. Anda and venga are also used in the sense of, "let's do it," or "that's right."

• Sale, de acuerdo, nos vemos a las seis.
  OK, alright, we'll see you at six.
• ¿Te pago la mitad ahora y lo demás después, vale?
  I'll pay you half now and the rest later, OK?