NFL clubs have different philosophies when it comes to free agency. Several jump aggressively, feet first, targeting their most coveted players and trying to sign them within the first 24 hours. Others slowly survey the market and wait for the 24-hour fallout period to end before making their move. And then there are teams that have very good depth, are close to winning their divisions and have a shot at winning the Super Bowl. They look for the bargain-basement deals to build a championship foundation.

Buyers must beware, though – there is a reason that these players are hitting the open market and are not being signed back by their current teams. A league source tells me that of the 2010 free-agent class of 51 players who signed four-year deals, only four remain under contract.

With free agency starting at 3 p.m. CT on Tuesday, March 12, clubs are currently restructuring player contracts and cutting overvalued veterans (cap casualties). Clubs that covet their own UFAs (unrestricted free agents) prepare to re-sign their own players before they hit the open market. All NFL clubs have worked to become compliant and must be under or at the mandated 2013 salary cap of $123,000,000 by March 12 at 2:59:59 p.m. CT. Teams now can “carry over” the remaining balance from the previous year’s unused cap – no matter the amount.

This will be the first year for a rule that was put in place prior to the free-agent period: Teams can reach out to agents to gauge interest in eligible UFAs. Previously, the combine represented the week where agents and front-office executives privately discussed the possibilities of deals. Now, such a window runs from March 9-12 March 9th, with the official free-agency period starting on Tuesday, March 12. Click here to see a comprehensive list featuring every free agent around the league.

The following information is provided by NFL Communication:

Clubs are permitted to contact, and enter into negotiations with, the certified agents of players who will become unrestricted free agents upon the expiration of their 2012 player contracts at 4:00 p.m. ET on March 12. However, a contract cannot be executed with a new club until 4:00 p.m. ET on March 12. During this negotiation period, a prospective unrestricted free agent cannot visit a club (other than the player’s current club) at its permanent facility or at any other location, and no direct contact is permitted between the player and any employee or representative of a club (other than the player’s current club). If a player is self-represented, clubs are prohibited from discussions with the player during the negotiating period. Clubs (other than the player’s current club) may not discuss or make any travel arrangements with prospective unrestricted free agent players, their certified agents, or anyone else associated with the player until the expiration of those players’ 2012 player contracts at 4:00 p.m. ET on March 12.

There are two different types of free agents: UFAs (unrestricted free agent) and RFA (restricted free agents. Below are the definitions for each category:

UFA – Any player with four or more accrued seasons at the expiration of his contract becomes a UFA. These players are completely free to negotiate and sign a contract with any organization, and clubs are free to negotiate without penalties or restrictions.

RFA – Any veteran player with three accrued seasons (but less than four accrued seasons) shall, at the expiration of his contract, become a RFA. These players come with restrictions; the players shall be completely free to talk with other clubs, but the club losing that player are allowed to counter the offer the player was given (First Refusal and or Draft compensation). The terms within the CBA get slightly tricky, and teams generally don’t lose RFAs through a bidding war. Rarely do teams mortgage future draft picks; however, while not popular, it does happen.

My top 15 free agents:

Mike Wallace – WR

Aqib Talib – DC

Cliff Avirl – DE

Cary Williams – DC

Andre Smith – OT

Dannell Ellerbe- ILB

Paul Kruger – DE

Steven Jackson – RB

Jared Cook – TEA

Phillip Wheeler – OLB

Dan Koppen – OC

Delaine Walker – TEA

William Moore – DB

Reggie Bush – OH

William Hayes – DE/DT