How can you gain proficiency in a skill after level 1?
I have been reading the Basic Rules a couple times, but could not find any way to gain proficiency in skills past level 1.
For example, if I create a Rogue, I may chose 4 skills among 11:
Acrobatics, Athletics, Deception, Insight, Intimidation, Investigation, Perception, Performance, Persuasion, Sleight of Hand and Stealth.
Now, a Criminal background grants proficiency in Deception and Stealth already, so I can pick 4 among 9:
Acrobatics, Athletics, Insight, Intimidation, Investigation, Perception, Performance, Persuasion and Sleight of Hand
which still leaves 5 of them on the floor.
I could find two nuggets:
The Human Variant Trait seems to allow to get proficiency in one skill.
The multi-classing rules (Chapter 6) seem to imply that one may get some proficiencies from multi-classing; though they refer to the PHB and do not specifically imply skill proficiencies (could be weapon or armor or tools...)
Are there other sources of skills that would allow one to broaden one's range of skills?
Also remember that this is a party game: one player _shouldn't_ have all of the skills. Rely on your companions (and let them shine). If you are playing a game with only one or two PCs, asking the DM for additional skills might be a reasonable way to help compensate.
@mattdm: Yes, of course, however the Rogue (specifically) has been up until now a "skill monkey" here to handle what the others did not. In my current (3.5e) party, I play both the roles of Scout and back-up Party Face for example, which requires mobility, perception and social skills on top of the usual stealth/traps/locks expected.
They and bards are still the skill-monkey's, but skill proficiencies alone are not what makes you good at a skill. Rogues and Bards get more skills than any other class, even if not by a large margin. In addition, rogues get the ability to double their proficiency bonus on a couple of skills. They are still elite in the skill arena.
Since it has inexplicably not been mentioned yet, I'll comment here to say that the Bard's level 2 feature Jack of All Trades makes being proficient in a skill a little bit less important, since it lets you add half your proficiency bonus to ability check rolls you're not proficient in (including rolls like initiative that have no proficiency you can gain). So dipping at least two levels into Bard might be a good way to improve your skill rolls, beyond the possibility of gaining new skill proficiencies (which you do also get from the class).
There are a few classes you can multiclass into to gain skills, such as Bard, Ranger or Rogue.
In addition to that, in the player's handbook there is a feat called "Skilled" which allows you to gain proficiency in any combination of 3 skills or tools.
There is also a bard ability in the college of lore that allows you to learn 3 more skills at level 3.
Currently, the downtime rules allow you to gain proficiency in tools but not skills.
In case it isn't clear, you don't have to pick skills from your class skill list when you gain new skills through the "Skilled" feat. You can pick any skill you want.
Given that downtime is essentially "free", I am not surprised about this restriction. Already, compared to 3.5e, the ability to learn languages "for free" (instead of spending a skill point) is great!
Downtime is, thankfully in this case, only as 'free' as the DM makes it. Many campaigns don't have a year or two worth of downtime throughout the entire campaign, and many more don't have more than 2 years. I like the fact that I can control pacing with this, and characters get something tangible out of the downtime, so I can have a campaign that stretches over a long period of time (which is more realistic to me anyway).
That depends on how the DM interprets that section. While many people interpret downtime as a reward resource thanks to the Adventurer's League, the wording on downtime could actually allow people to choose how much time they spend on other things and manually play out that time spent outside of adventuring.