Correct AesCryptoServiceProvider usage

I'm trying to write some straight forward encryption routines. Here's what I've been able to come up with based on searching the Web.

public string Encrypt(string plainText)
{
    byte[] encrypted;

    // Create an AesCryptoServiceProvider object
    // with the specified key and IV.
    using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
    {
        // Create an encryptor to perform the stream transform.
        ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

        // Create the streams used for encryption.
        using (MemoryStream msEncrypt = new MemoryStream())
        {
            msEncrypt.WriteByte((byte)aesAlg.Key.Length);
            msEncrypt.Write(aesAlg.Key, 0, aesAlg.Key.Length);
            msEncrypt.WriteByte((byte)aesAlg.IV.Length);
            msEncrypt.Write(aesAlg.IV, 0, aesAlg.IV.Length);

            using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
            {
                using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                {
                    //Write all data to the stream.
                    swEncrypt.Write(plainText);
                }
                encrypted = msEncrypt.ToArray();
            }
        }
    }
    return Convert.ToBase64String(encrypted);
}

public string Decrypt(string cipherText)
{
    string plaintext = null;

    using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
    {
        // Create the streams used for decryption.
        using (MemoryStream msDecrypt = new MemoryStream(Convert.FromBase64String(cipherText)))
        {
            int l = msDecrypt.ReadByte();
            byte[] key = new byte[l];
            msDecrypt.Read(key, 0, l);
            l = msDecrypt.ReadByte();
            byte[] IV = new byte[l];
            msDecrypt.Read(IV, 0, l);

            // Create a decryptor to perform the stream transform.
            ICryptoTransform decryptor = aesAlg.CreateDecryptor(key, IV);

            using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
            using (StreamReader srDecrypt = new StreamReader(csDecrypt))
            {

                // Read the decrypted bytes from the decrypting stream
                // and place them in a string.
                plaintext = srDecrypt.ReadToEnd();
            }
        }
    }
    return plaintext;
}

Two questions:

• First, most of the examples I found hard coded the Key and IV. So what I'm doing is writing it to the encrypted bytes. This will make my encrypted data larger. Is there a better way?
• Also, I'm not using any password. Would one use a password to generate a custom Key? And, if so, how would I know how long that key needed to be?