In no case shall judgment be rendered against any defendant unless upon service, or acceptance or waiver of process, or upon an appearance by the defendant, as prescribed in these rules, except where otherwise expressly provided by law or these rules.
When a party asserts a counterclaim or a cross-claim against another party who has entered an appearance, the claim may be served in any manner prescribed for service of citation or as provided in Rule 21(a). Section 6. Costs and Security Therefor