The first thing you always want to do is check with the Dungeon Master to see if there is any special information that he/she may have for you for the new campaign. See what the DM things, how he/she feels the campaign is going to flow... Will it be a rough-and-dirty campaign? Rich in magic? Full of political intrigue? The kind of campaign the DM intends to run will help you determine what kind of character you may have the most enjoyment playing. If the DM is going to run a Dungeon Crawl campaign, a ranger or druid doesn't fit as well as a rogue or fighter might.
We're all here to have fun, so the most important thing you need to do is create a character that has a reason to be risking their life adventuring with a good-aligned party!
For each campaign, the Dungeon Master will make available a list of available character classes that will be allowed to form a well-balanced party. For special campaigns, he may decide that there will be no magic-users, or that there are no barbarians in this region. Usually though, this is just an effort to prevent the party from having four rogues, two mages, and no fighters or clerics! See what's available for the Silverymoon Campaign!
Once you have chosen what class you want to play, you need to decide a couple other things before continuing. First, you need to choose what race you want to play. Just like the class list, the Dungeon Master will have a race list for you to select what you want to play. The DM may or may not have restrictions on this, depending on the campaign and/or the cosmopolitan make-up of the world/region. Be sure to check with the DM as to what kinds of consequences may come of your decision.
Now that you've decided what race and class your character is going to be, try to come up with a simple character concept to help you through the rest of the creation. If you want to make a bash-in-the-door-and-kill-them barbarian, then you know to take as many power-driven feats and skills as you can. If you want to play a deft swashbuckler with a knack for charm and diplomacy, you know to take feats such as weapon finesse and improved initiative, and skills such as bluff, diplomacy, and knowledge (nobility - etiquette). Deciding on a character name now might help you start to piece together who you want this person to be.
Use the standard method for generating ability scores: roll 4d6 six times, dropping the lowest die from each total, and assign the scores to the abilities. This must be done in front of the DM, or it never happened at all. If you're not satisfied with the rolls, you may throw out the entire set and make another.
Once you've assigned your rolled ability scores, modify them for your race as per the PHB or FR3E Campaign book. These will be your starting ability scores, remember that you can raise an ability score every four levels.
Before customizing your character with Skills and Feats, you should record your racial and class features on your character sheet. Don't forget your base attack and save bonuses, as well as starting hit points. This will help you realize where your starting strong points are and will help you decide where to take your character.
Just as important as what your character can do, is how he/she got there. Please visit the Creation Points System page for more help on bringing your character to life. By defining and establishing your character, in such a way as to make your effort to roleplay apparent, you are rewarded in such a way that benefits your character.
You'll want to choose your character's starting skills to get an idea of what your new character is capable of. There are many skills that can be used without ranks, but don't forget to apply some ranks to skills that are helpful no matter what your class is (i.e. spot, listen).
Your character's feats are their strongest abilities outside their class features. With the selection of feats available, this can be more difficult than you may think. If you know the direction you want to take with your character, it is a good idea to plan what feats you may be taking and when... while you may not want to plan out your entire character's future, this is good if you intend to take feats that have prerequisites.
Equip your character with the starting funds and prices as listed in the PHB. Record your all equipment and weights on your character sheet, and total your weight to determine your encumbrance. Don't forget the necessities like toiletries, rations, watserskins, spare clothes, etc.
So you've recorded your abilities, features and base combat abilities, skills, feats, and equipment. Now you get to figure out the rest of the numbers. First, figure in any equipment as needed. This includes your armor bonus to your total AC, and your weapon statistics. Apply your ability score modifiers to your saves, combat bonuses, armor class, and skills. Total all contributing bonuses to get your total modifiers. Don't forget to apply things like your max Dex bonus and Armor check penalties.
Getting all of the numbers finished on the sheet isn't what makes a character. Now you have to do the juicy stuff. Your character's personality is yours to create in game, but you can determine his appearance now. If you've already used the Creation Points System Background option of Physical Description, you've got this half done!