http://philosophy.hku.hk/think/arg/goodarg.php

Criterion #1 : A good argument must have true premises
Criterion #2 : A good argument must be either valid or strong
Criterion #3 : The premises of a good argument must not beg the question
Criterion #4 : The premises of a good argument must be plausible and relevant to the conclusion

Conclusion: A good argument is an argument that is either valid or strong, and with plausible premises that are true, do not beg the question, and are relevant to the conclusion.