http://www.agoracom.com/ir/patriot/message/527077

is a good summary, but to answer you:

http://209.85.135.104/search?q=cache:DwI4M7vkx9wJ:www.sfvba.org/memberresources/barnotes/2005/SFVBAMar05.pdf+westlaw+suer&hl=en&ct=clnk&cd=28

the injury must be either to the person of the suer

http://www.vlex.us/caselaw/Supreme-Court-of-Georgia/HORNBUCKLE-by-Next-Friend-v-PLANTATION-PIPE-LINE-COMPANY/2100-20418607,01.html

cross-complaint
n. after a complaint has been filed against a defendant for damages or other orders of the court, the defendant may file a written complaint against the party suing him/her or against a third party as long as the subject matter is related to the original complaint. The defendant's filing of a complaint is called a cross-complaint, and the defendant is then called a cross-complainant and the party he/she sues is called a cross-defendant. The defendant must still file an answer or other response to the original complaint. If the cross-complaint is against the original plaintiff (original suer) then it can be served on the plaintiff's attorney by mail, but a third party must be served in person with the cross-complaint and a new summons issued by the clerk of the court. The cross-defendants must then file answers or other responses. These are called pleadings and must be carefully drafted (usually by an attorney) to properly state the factual as well as legal basis for the claim and contain a prayer for damages or other relief.

default judgment
n. if a defendant in a lawsuit fails to respond to a complaint in the time set by law (commonly 20 or 30 days), then the plaintiff (suer) can request that the default (failure) be entered into the court record by the clerk, which gives the plaintiff the right to get a default judgment. If the complaint was for a specific amount of money owed on a note, other money due, or a specific contract price (or if the amount due is easy to calculate) then the clerk of the court can enter a default judgment. If proof of damages or other relief is necessary, a hearing will be held in which the judge determines terms of the default judgment. In either case the defendant cannot speak for himself/herself. A defendant who fails to file an answer or other legal response when it is due can request that the default be set aside, but must show a legitimate excuse and a good defense to the lawsuit.

frivolous
adj. referring to a legal move in a lawsuit clearly intended merely to harass, delay or embarrass the opposition. Frivolous acts can include filing the lawsuit itself, a baseless motion for a legal ruling, an answer of a defendant to a complaint which does not deny, contest, prove or controvert anything, or an appeal which contains not a single arguable basis (by any stretch of the imagination) for the appeal. A frivolous lawsuit, motion or appeal can result in a successful claim by the other party for payment by the frivolous suer of their attorneys' fees for defending the case. Judges are reluctant to find an action frivolous, based on the desire not to discourage people from using the courts to resolve disputes.

http://dictionary.law.com/default2.asp?selected=794&bold=suer||

A lawyer I'm not, but I did use my LL.M to upgrade to a PhD.

Be well