Good question. I assume you ask because conscientiousness is highly correlated with a number of positive life outcomes?

1. Conscientiousness is temporally stable, that is, in the average individual, it does not much change over time.
2. Conscientiousness is linked to a number of other personality traits - e.g. self-regulation, perseverance, etc.... These traits can be trained; and according to a quick skim of the study below, training those traits in turn effects conscientiousness, at least in children.

http://www.sas.upenn.edu/~duckwort/images/publications/EisenbergDuckworth_ConscientiousnessOriginsinChildhood_2012.pdf

1. In adults, the trait is more temporally stable (sorry, no citation off hand), but there are hacks - e.g. self-control strategies like mental contrasting, implementation intentions, learned industriousness, etc... can partially achieve the same effect as having more conscientiousness.

This is a good question though... I will investigate some more.