Any skill that gets its own heading in the Basic Set – even just a pointer (as for Airshipman on p. B174, Axe/Mace on p. B179, and Captivate on p. B183) – counts as one skill when applying Cost of Talent (p. 4) and Smooth Talent Cost (p. 25).
There are wrinkles, though:

　Specialties: If a skill has specialties (pp. B169-170), then no matter how many there are or how many the Talent affects (one, some, all), it counts as one skill.
Specialties are easy to distinguish – they don’t get their own headings, but are instead discussed under a master heading that’s marked with a dagger (†).

Details typically follow the words “you must specialize.” While Talents mostly prescribe required specialties, all this is equally valid for any optional specialties specified.

Expert Skills (pp. B193-194) overlap so much with other skills, and Hobby Skills (p. B200) and Sports (p. B222) have such limited game utility, that each of these classes is considered a single skill with specialties.

　Grouped Skills: Some skills have brief headings without description and are actually described beneath a collective heading; see Grouped Skills (p. B169).
Examples include Acrobatics (p. B174), Crewman (p. B185), Enthrallment (pp. B191-192), Environment Suit (p. B192), Melee Weapon (pp. B208-209), and Professional Skill (p. B215).
These usually count as separate skills.
An exception is when a Talent affects several of these but few PCs will learn more than one.
In that case, treat them as one skill; e.g., the way Superior Equilibrioception (p. 16) handles Acrobatics, Aerobatics, and Aquabatics.

　 Where different skills fill the same role in different campaigns, and won’t normally coexist, a Talent may list them on an “either/or” basis, counting them as one skill; e.g., Psientist (p. 15) and its handling of Expert Skill (Psionics) and Hidden Lore (Psionics).

　If a skill only sometimes enjoys the Talent’s bonus, treat the bonus as an alternative benefit (pp. 18-19), not as one of the Talent’s skills; this is how Street-Smart (p. 16) handles Tracking in cities (Tracking is primarily a wilderness skill!), and how Seafarer (p. 14) treats Carousing and Streetwise in ports (most territories have more interior than coast).

　 However, if the condition is merely a reminder to use appropriate tools or methods, then the skill counts.
For instance, Forced Entry is a full skill for Mr. Smash (p. 13), because a “swung two-handed weapon” – like the classic crowbar – is standard (but the Intimidation bonus is conditional, as weapons often aren’t handy in social situations).