Mergers and acquisitions have always been big business opportunities for law firms, but now it seems that legal businesses are turning this attention on themselves. The drive towards creating a more corporate profession has led to a boom in law firm mergers, resulting in the creation of ever-larger practices. Recent announcements, such as Irwin Mitchell's plans to merge with Scots firm Golds to form a 1,200 fee earner superfirm, or south Yorkshire's Atteys' decision to join forces with local rival Richmonds, show that many believe big is beautiful.

A merger announcement is, however, just a small part of taking two separate organisations and turning them into one successful business. The logistical and cultural challenges this presents are not for the faint-hearted and require management and planning long before and after the physical merger has taken place. What any firm considering this course of action must do first is ask itself why it is doing so and what it wants to achieve.

Reasons given most frequently are plans to increase turnover, improve profitability and prospects for growth and increase a firm's attractiveness to lucrative clients. What underlies these financial objectives, however, is the suggestion that the two firms can do better business together than they can apart. Perhaps they have areas of expertise that complement one another or could form an organisation of sufficient critical mass to land bigger clients. Ensuring this is a success from the word go means firms must find a compatible merger partner with a culture and outlook that dovetails with their own.

Tim Foster, UK managing partner of Reed Smith Richards Butler, which formed a $900m (£450m), 1,500-lawyer firm following the merger of US-based Reed Smith with London's Richards Butler, agrees. He says: "A genuine meeting of minds between firms means a merger can start as a marriage rather than a takeover."

This is certainly the case if the resulting operation has been created, as with Reed Smith Richards Butler, to consolidate a business's activities across international boundaries. Foster continues: "From the outset, both firms were convinced that it would give them a lift in crucial areas. As a US firm, Reed Smith had the international dimension, but its relatively low profile in London limited its ability to take advantage of UK opportunities for US clients. Meanwhile, Richards Butler's strong presence in London stood to benefit from stronger links with overseas territories. Merging allowed us to consolidate and strengthen the business as a whole."

At Vizards Tweedie, a City-based general practice formed from the 2004 merger of two established firms, Vizards Oldham and Tweedie Prideaux, our management teams set out to accomplish something similar. This merger brought together complementary expertise in property, commercial, private client and litigation specialisms. But even though there were solid strategic reasons behind the merger, they needed to be communicated sensitively to the individuals who worked in both firms. Cultural change can be a stressful business, which can have an impact on business performance in a people-based profession such as the law.

Avoiding this meant encouraging everyone involved to view the success of the merger as a collective responsibility. Setting up cross-firm working groups to oversee certain aspects of the merger not only spread the workload associated with making it happen more evenly but also encouraged integration and teamworking. This meant that once the merger was complete we were also able to merge teams, thereby making the business more efficient, while averting the creation of a corrosive 'them' and 'us' culture.

This view is echoed by Michael Shaw, managing partner of regional heavyweight Cobbetts, itself a merger veteran that has grown its operations in Leeds, Manchester and Birmingham by canny acquisition. He said: "A merger never ends on the day of the merger – it also helps to have a plan for the following two or three years – especially if you want to avoid the psychological trough which often happens a few months in. Remember that some people will always take the 'loss' of the firm they worked for as a personal bereavement."

Cobbetts' determination to avoid this has seen it engage not only a company specialising in 'organisational development' but also a staff psychologist to support staff and provide training and coaching to managers. Yet its focus on developing people skills backs up ambitious plans to grow quickly and pick up regional business from national firms preoccupied with developing their London and international networks.

Shaw adds: "For this reason we consciously never choose merger partners who are more than 30% of our firm's total size, as we believe [firms under this threshold] can be comfortably absorbed into Cobbetts as a whole."

One of the big challenges in the merging or absorption period is ensuring that, where there is a cultural fit, working and administrative practices also knit together. A merger is a major opportunity for change and often provides the impetus for upgrading systems and making efficiencies. Principally, it creates the conditions for a bigger legal force, which can work well with a smaller administration team. The planning period ahead of a merger is the only time in which a firm can really assess how its administrative 'engine room' is run and where rationalisation can be made. Remember that savings made here can provide the financial clout required to afford efficient new systems or to move to new premises.

Grant Thornton's Gary Harding cautions: "Mergers can often see more than 50% more fee earners join a firm at one time, so the culture and associated support services must grow and adapt accordingly.

"The track record of shareholder value in corporate takeovers is not great and more than half see their value drop significantly. There is no reason to think that the merger of professional firms should deliver better results, unless the process is thought through and managed very carefully."

Looking back again to how we managed the merger that formed Vizards Tweedie, we also used this as an opportunity to examine our costs – primarily as the new firm was set to move into new premises. Here, we identified that, with each square foot of a London office commanding a high price, it made strong commercial sense for us to engineer a situation in which we could house more fee earners and complete more support work off-site.

This led us to go down the outsourcing path, sending work to legal transcription specialist Voicepath through our existing digital dictation system. It works just as effectively as an internal typist, but being a UK-based service also means that even though we are employing fewer secretaries ourselves, jobs themselves are not being sent overseas. Outsourcing, therefore, is an example of how making efficiencies during a merger can have clear financial benefits, in that, by freeing up space for fee earners, it allows us to bill more per workstation and keep overheads under control in a competitive market.

Fundamentally, the secret to a successful merger is the same as running a flourishing business. It must be well-planned, with clear strategic objectives, but never forgetting that it is the efforts and support of individuals and their goodwill that actually delivers results. People are surprisingly adaptable and, provided they are kept informed and their views are heard, can easily be convinced that, as Foster says, "the merger is good for the business rather than just more money for the partners".

For many law firms a merger is the best and quickest way to step up a gear. Life in a faster lane has its risks but it is also hugely exciting for the profession as it finally catches up with the rest of the corporate world.

Ron Perry is senior partner of Vizards Tweedie.