Is 638 credit score good enough for a .......?

Question

for a major credit card?

Answer 1

Depending on the negatives on your reports, with that score you may be qualified for cards from Orchard Bank, HSBC and possibly Hooters (yes Hooters has a major credit card lol)

Keep in mind that those cards may or may not come with annual fees. (generally from $30 to $75 a year, rarely over $75/year)
After having the card for a year, and keeping it in good standing and no new negatives on your reports, they may waive the annual fee if you request it.

edited to add after seeing your other question:
Dependent on the rest of your credit history and who you have cards with now, Citi may be hard to get with their major credit cards, though you may be able to qualify for their store backed cards.

Answer 2

If you can get it up above 680, you'll be a lot better off.

720+ = Excellent credit. You should have no problems as most loan programs will be available to you.
680 - 719 = Good credit. You should have few problems depending on what product you seek.
620 - 679 = Lender has to take a closer look at your file but should be able to qualify you for a loan. Some products may not be available.
570 - 619 = Higher risk; you will not be eligible for the best rates and products. Products will be limited.
Below 570 = Very high risk. Products will be limited and other factors will need to be considered.

Answer 3

For getting any kind of loan Credit History is much more important than credit score. Often, the lack of credit history is equated with bad credit. You should be aware that lenders will go through your credit report once you apply for loan for buying a house. Therefore you should polish your credit report. Anyway, in order to establish a good credit history and at the same time risen your credit score in a short time do following things:

1) Close all of your credit cards but one. It reflects in your credit report and it is a very good sign. For instance say that you have 5 credit cards with $1000 credit limit for each. Therefore you are responsible for $5000 of possible debt. But when you close 4 of them, now you are only responsible for $1000 of debt which lowers the level of risk of lending money to you.

2) If you have any loan, like car loan or any balance on your credit cards, try to pay more than your monthly payment for 6 months or something. I mean say your monthly due on your car loan is $150, try to pay $250 each month. Lenders can see these trends in your credit report and they see that you’re a responsible borrower.
If you don’t have such loans, I suggest getting a $3000-$4000 loan and paying it off in full in 5-6 months. You might pay $200-$300 of interest but you will save thousands of dollars in your home mortgage and interest rates.

Also checkout http://www.howtoestablishgoodcredit.com/Credit_Articles/index.php
There are lots of articles there, related to your question, which you can find useful to boost your credit.