From the sorcerer page:
Skill Ranks per Level: 2 + Int modifier.
Since the modifier for an 18 int is +4 (source), that means you get 6 skill points. If you choose Sorcerer as your favored class, you may choose to get one extra skill point OR one extra hit point.
As a first-level character, you have 1 HD. Therefore, you can only put up to one rank in each skill:
You can never have more ranks in a skill than your total number of Hit Dice.
If you put a rank into any of the sorcerer class skills, however, you gain an extra +3 bonus on your check with that skill. The sorcerer class skills are:
Appraise (Int), Bluff (Cha), Craft (Int), Fly (Dex), Intimidate (Cha), Knowledge (arcana) (Int), Profession (Wis), Spellcraft (Int), and Use Magic Device (Cha).
Some sample calculations
Let's run down some scenarios, for completion's sake. If you put skill ranks into, say, Appraise, Craft (something), Knowledge (arcana), and Spellcraft, your total modifier for each of those skills would be:
1 rank + 3 for class skill + 4 int bonus = 8
and you would roll 1d20+8 to use each of those skills.
If you put one rank into Bluff, you would have:
1 rank + 3 for class skill + 2 cha bonus = 6
so you'd only roll 1d20+6 for a Bluff check.
If you put one rank into Knowledge(nature), which is not a class skill for Sorcerer, your total would be:
1 rank + 4 int bonus = 5
so you'd roll 1d20+5.
If you don't put any ranks into Acrobatics, which is also not a class skill but can be used untrained, you would roll:
0 ranks + 1 dex bonus = 1
If you don't put ranks into Appraise, you don't get the class bonus either, so you'd roll:
0 ranks + 4 int bonus = 4
1d20+4 for a check.
I hope that helps!