The restaurant business is a tough game – according to a study by Cornell University about 30% fail in their first year. So it’s not surprising that some restaurants have a range of tactics to keep costs down and diner numbers up. While most restaurants don't trick or cheat guests, here are some of the ways the less ethical places do.

Think twice about asking for lemon slices in your drink. Studies have found that nearly 70% of lemon wedges in restaurants contain up to 25 different types of germs, including E.coli and contamination from raw meat.

Making an effort with your appearance could be the key to getting better service. A study earlier this year suggested that wait staff are more attentive to those who are well-dressed than scruffy diners.

In many kitchens, there are usually fries being cooked on a constant loop, but they aren't always a fresh batch. To ensure your fries are fresh out of the fryer, ask for no salt – this will require staff to put on a separate batch just for you.

Because everyone wants to eat lunch at the same time – with a relatively small window in which to do it – restaurants are likely to stagger bookings, keep you waiting for your table, or get waiting staff to chat to you in order to help the kitchen take the strain.

Tipsy diners or those looking to impress their companions tend not to peruse the bill before paying. Restaurant staff know this so some unethical waiters may add extra items without the customers knowing.

Those tomato wedges and sliced peppers may not have been sliced on the day of your visit. At some restaurants, salad bar items that aren't used one day are stored in a refrigerator and just reused the next day. And the next. At least they're preventing food waste...

It doesn’t go unnoticed if you’re impolite to staff – many restaurants keep a note of difficult customers and it could prevent you from getting future reservations.

You may not be able to afford to spend a fortune on an upmarket meal, but you could be getting better value for money if you do. Ingredients, staff, linen, flowers and rent are all be factored into the pricing of dishes. So when you think you’re getting a bargain for a pizza that costs very little to make, it’s often had a huge mark-up compared to the tighter margins fine dining restaurants work within.

Why should it? In unscrupulous restaurants, what’s left in the bottle you bought might be re-sold, by the glass, the next day.

A lot of menus are designed in such as way that your choices are pretty much decided for you – and you won’t even be aware of it. Examples of this are dishes that are ‘boxed-out’ or placed in the top right-hand corner to catch your eye.

In order to cover commission charges taken by some online food delivery companies, restaurants have been known to mark-up items. Customers can end up paying two thirds more when they order the same food through a delivery service than if they eat it in the restaurant.

Ice machines are extremely difficult to clean. Avoid taking a look inside one if you like your drinks chilled...

Lots of side dish orders are money-spinners because they don’t cost much to make and they’re quick and easy to prepare.

The same goes for vegetarian dishes, or soups, which tend to be cheaper to make than protein-heavy dishes.

Pasta dishes can be marked up to 10 times their cost, though this profit is reduced if the pasta is made from scratch in-house.

This doesn’t apply to all restaurants, though some do it. The specials board is often a means for the kitchen to use up food it over-ordered or that’s close to its use-by date. It’s not always the case though – often it offers genuine specials using produce recommended by good suppliers that morning.

The second-cheapest wine often has the highest mark-up because it’s what customers order in an attempt to not look cheap by opting for the house selection. Wine is often the largest expense for diners. It’s perfectly normal for restaurants to put a 200–300% mark-up on a bottle though 'the more expensive the wine, the better the value it is to the customer.'

An increasing number of restaurants don’t take bookings or only offer a small number of reservations. This is partly because those who book and then don't show up can seriously damage a restaurant's takings. It also means places can ‘turn a table’ three times with walk-in diners because customers who book tend to stick around for longer. This policy can work against restaurants, however – it can be harder to move diners on if there’s no subsequent booking for their table.

Apparently, people who book by email are less likely to show up so restaurants prefer customers who call to reserve a table. People who book via email are also harder to track down if they leave without paying.

It’s a sad truth, but chefs are still mainly men. In the UK, only 20% of chefs are women and in the US – according to data gathered by Bloomberg – just 6.3% of head chefs are women.

Marco Pierre-White may have given his three Michelin stars back, but most chefs will covet a star because it (nearly) always ensures success. One is good, two is great and three means the restaurant can charge whatever it likes.

Up to 90% of a dining venue’s profits can be made during the festive season when more expensive items such as champagne are sold. This can make the most wonderful time of the year the busiest and most lucrative for many restaurants.

Many restaurants will only open their phone lines at certain times of the day to take bookings so check the websites before trying to ring. If there's no dedicated time, it's best to ring in the morning before lunch service or mid-afternoon before dinner service to get on the good side of the front of house staff. Chances are that if you call during service, no one will pick up.

The long-hours culture of restaurant work can take its toll on staff. This year, trade union Unite found that 69% of chefs said long working hours affected their health, with many turning to alcohol and other stimulants to get them through a shift. Last year, Gordon Ramsay highlighted the widespread use of cocaine in the hospitality industry.

Many restaurants try and upsell, offering diners special meal deals, pricier wines or the chance to 'super-size' dishes. For those who give in to the sales technique, the bill increases by an average of 17%. And it's not just your wallet that will be hit. Upselling can also mean diners consume 55% more calories.

Chefs are constantly sampling and tweaking dishes during service. While we hope this is rare, some lazy chefs re-use the same spoon without washing after each use and apparently some have been known to employ a 'lick and stick' technique to attach garnishes. Gross.

Chefs work hard, as all restaurant staff do, but they’re not spoiled at mealtimes – they rarely get to eat the same food as diners.